Emc Fc4500 Users Manual Fibre Channel Storage Systems S FC4500, FC5300, And FC5700 CONFIGURATION PLANNING GUIDE

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EMC Fibre Channel Storage Systems Models FC4500, FC5300, and FC5700 CONFIGURATION PLANNING GUIDE

EMC Enterprise Storage

EMC Corporation 171 South Street, Hopkinton, MA 01748-9103

Corporate Headquarters: (508) 435-1000, (800) 424-EMC2 Fax: (508) 435-5374 Service: (800) SVC-4EMC

EMC Fibre Channel Storage Systems

Models FC4500, FC5300, and FC5700

CONFIGURATION PLANNING GUIDE

P/N 014003039-02

EMC Fibre Channel Storage Systems Configuration Planning Guide

Printed May 2001

No part of this publication may be reproduced or distributed in any form or by any means, or stored in a

database or retrieval system, without the prior written consent of EMC Corporation.

The information contained in this document is subject to change without notice. EMC Corporation assumes

no responsibility for any errors that may appear.

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furnished under a license, and may be used or copied only in accordance with the terms of such license.

EMC either owns or has the right to license the computer software programs described in this document.

EMC Corporation retains all rights, title and interest in the computer software programs.

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Trademark Information

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All other trademarks mentioned herein are the property of their respective owners.

EMC Fibre Channel Storage Systems Configuration Planning Guide

iii

Preface..............................................................................................................................xi

Chapter 1 About Fibre Channel Storage Systems and Networks

(SANs)

Introducing EMC Fibre Channel Storage Systems.......................1-2

Fibre Channel Background..............................................................1-3

Fibre Channel Storage Components ..............................................1-4

Server Component (Host-Bus Adapter Driver Package with

Software).....................................................................................1-4

Interconnect Components ........................................................1-4

Storage Component (Storage Systems, Storage Processors

(SPs), and Other Hardware).....................................................1-9

Types of Storage System Installations..........................................1-10

About Switched Shared Storage and SANs (Storage Area

Networks) ........................................................................................1-11

Storage Groups.........................................................................1-12

Storage System Hardware for Shared Storage ....................1-15

About Unshared Storage ...............................................................1-16

Storage System Hardware for Unshared Storage ...............1-16

Chapter 2 RAID Types and Tradeoffs

Introducing RAID.............................................................................2-2

Disk Striping...............................................................................2-2

Mirroring.....................................................................................2-2

RAID Groups and LUNs ..........................................................2-3

RAID Types........................................................................................2-4

RAID 5 Group (Individual Access Array) .............................2-4

RAID 3 Group (Parallel Access Array)...................................2-5

Contents

EMC Fibre Channel Storage Systems Configuration Planning Guide

Contents

RAID 1 Mirrored Pair ...............................................................2-7

RAID 0 Group (Nonredundant Array) ..................................2-8

RAID 1/0 Group (Mirrored RAID 0 Group).........................2-8

Individual Disk Unit .................................................................2-9

Hot Spare ....................................................................................2-9

RAID Benefits and Tradeoffs.........................................................2-12

Performance .............................................................................2-13

Storage Flexibility....................................................................2-14

Data Availability and Disk Space Usage..............................2-14

Guidelines for RAID Types ...........................................................2-17

Sample Applications for RAID Types..........................................2-19

Chapter 3 Planning File Systems and LUNs with Shared Switched

Storage

Dual Paths to LUNs..........................................................................3-2

Sample Shared Switched Installation ............................................3-3

Planning Applications, LUNs, and Storage Groups....................3-6

Application and LUN Planning ..............................................3-6

Application and LUN Planning Worksheet ..........................3-7

LUN and Storage Group Planning Worksheet .....................3-8

LUN Details Worksheet..........................................................3-11

Chapter 4 Planning LUNs and File Systems with Unshared Direct

Storage

Dual SPs and Paths to LUNs...........................................................4-2

Unshared Direct and Shared-or-Clustered Direct Storage .........4-2

Sample Unshared Direct Installation......................................4-2

Sample Shared-or-Clustered Direct Installation...................4-3

Planning Applications and LUNs..................................................4-4

Application and LUN Planning ..............................................4-4

Application and LUN Planning Worksheet ..........................4-5

LUN Planning Worksheet........................................................4-6

Completing the LUN Details Worksheet.............................4-12

Chapter 5 Storage System Hardware

Hardware for Shared Storage .........................................................5-3

Storage Hardware — Rackmount DPE-Based Storage

Systems .......................................................................................5-3

Disks............................................................................................5-4

Storage Processor (SP) ..............................................................5-5

EMC Fibre Channel Storage Systems Configuration Planning Guide

Contents

Hardware for Unshared Storage.................................................... 5-6

Types of Storage System for Unshared Storage ................... 5-6

Disks............................................................................................ 5-8

Storage Processor (SP).............................................................. 5-9

Planning Your Hardware Components ...................................... 5-11

Configuration Tradeoffs - Shared Storage .......................... 5-11

Configuration Tradeoffs - Unshared Storage ..................... 5-12

Hardware Data Sheets................................................................... 5-14

DPE Data Sheet........................................................................ 5-14

iDAE Data Sheet...................................................................... 5-16

DAE Data Sheet....................................................................... 5-18

Cabinets for Rackmount Enclosures............................................ 5-20

Cable and Configuration Guidelines .......................................... 5-21

Hardware Planning Worksheets .................................................. 5-24

Hardware for Shared Storage ............................................... 5-24

Hardware Component Worksheet for Shared Storage...... 5-25

Hardware Component Worksheet for Shared Storage...... 5-27

Hardware for Unshared Storage .......................................... 5-27

Hardware Component Worksheet for Unshared Storage. 5-30

Hardware Component Worksheet for Unshared Storage. 5-31

Hardware Component Worksheet for Unshared Storage. 5-33

Hardware Component Worksheet for Unshared Storage. 5-35

Chapter 6 Storage-System Management

Using Navisphere Manager Software ........................................... 6-3

Storage Management Worksheets.................................................. 6-5

Index ................................................................................................................................i-1

EMC Fibre Channel Storage Systems Configuration Planning Guide

Contents

EMC Fibre Channel Storage-System Configuration Planning Guide

vii

1-1 Storage System Models ................................................................................ 1-2

1-2 Nodes - Initiator and Target ....................................................................... 1-3

1-3 Switch and Hub Topologies Compared .................................................... 1-6

1-4 A Switch Zone ............................................................................................... 1-7

1-5 16-Port Switch, Back View .......................................................................... 1-7

1-6 Nine-Port Hub .............................................................................................. 1-8

1-7 Disk-Array Processor Enclosure (DPE) ..................................................... 1-9

1-8 Types of Storage System Installation ....................................................... 1-10

1-9 Components of a SAN ............................................................................... 1-11

1-10 Sample SAN Configuration ...................................................................... 1-13

1-11 Data and Configuration Access Control with Shared Storage ............ 1-14

1-12 Storage System with a DPE and Three DAEs ........................................ 1-15

1-13 Storage System Hardware for Unshared Storage .................................. 1-17

2-1 Multiple LUNs in a RAID Group ............................................................... 2-3

2-2 RAID 5 Group ............................................................................................... 2-5

2-3 RAID 3 Group ............................................................................................... 2-6

2-4 RAID 1 Mirrored Pair .................................................................................. 2-7

2-5 RAID 1/0 Group (Mirrored RAID 0 Group) ............................................ 2-9

2-6 How a Hot Spare Works ............................................................................ 2-11

2-7 Disk Space Usage in the RAID Configurations ...................................... 2-16

3-1 Sample Shared Switched High Availability installation ........................ 3-3

4-1 Unshared Direct Installation ....................................................................... 4-2

4-2 Sample Clustered Installation ..................................................................... 4-3

5-1 Shared and Unshared Storage .................................................................... 5-2

5-2 DPE Storage-System Components – Rackmount Model ........................ 5-3

5-3 Rackmount System with DPE and DAEs .................................................. 5-4

5-4 Shared Storage Systems ............................................................................... 5-5

5-5 Storage System Types for Unshared Storage ........................................... 5-7

5-6 DPE Components - Deskside Model ......................................................... 5-8

5-7 Disks and Disk IDs ....................................................................................... 5-9

Figures

viii

EMC Fibre Channel Storage-System Configuration Planning Guide

Figures

5-8 Storage System with Two SPs Connected to the Same Server ............. 5-10

5-9 Storage System with Two SPs Connected to Different Servers ............ 5-10

5-10 Comparison Between Optical and Copper Cabling ............................... 5-21

5-11 Cable Identifier — DPE-Based System for Shared Storage ................... 5-24

5-12 Sample Shared Storage Installation .......................................................... 5-26

5-13 Cable Identifier — Unshared System without Hubs ............................. 5-28

5-14 Cable Identifier — Unshared Full-Fibre System with Hubs ................. 5-29

5-15 Sample Unshared Deskside System — Basic Configuration ................ 5-31

5-16 Sample Unshared Deskside System — Dual-Adapter/Dual-SP

Configuration ............................................................................................... 5-32

5-17 Sample Component Worksheet for DPE-Based System with Hubs — Two

Loops.............................................................................................................. 5-34

6-1 Sample Shared Switched Environment with Navisphere Manager ...... 6-4

6-2 Sample Unshared Environment with Navisphere Manager .................. 6-4

EMC Fibre Channel Storage-System Configuration Planning Guide

2-1 Performance, Availability, and Cost of RAID Types

(Individual Unit = 1.0) ............................................................................... 2-13

3-1 Cache Recommendations for Different RAID Types ............................ 3-16

4-1 Cache Recommendations for Different RAID Types ............................ 4-15

5-1 High-Availability Options, Deskside Unshared Storage ...................... 5-13

5-2 High-Availability Options, Rackmount Unshared Storage ................. 5-13

5-3 Cable Sizes — Optical ............................................................................ 5-22

5-4 Cable Sizes — Copper ................................................................................ 5-23

Tables

EMC Fibre Channel Storage-System Configuration Planning Guide

Tables

EMC Fibre Channel Storage-System Configuration Planning Guidexi

Preface

This planning guide provides an overview of Fibre Channel

disk-array storage-system models and offers essential background

information and worksheets to help you with the installation and

configuration planning.

Please read this guide

•if you are considering purchase of an EMC Fibre Channel

disk-array storage system and want to understand its features; or

•before you plan the installation of a storage system.

Audience for the Manual

You should be familiar with the host servers that will use the storage

systems and with the operating systems of the servers. After reading

this guide, you will be able to

•determine the best storage system components for your

installation

•determine your site requirements

•configure storage systems correctly

xii

EMC Fibre Channel Storage-System Configuration Planning Guide

Preface

Organization of the Manual

Chapter 1 Provides background information on the Fibre

Channel protocols and explains the major installation

types.

Chapter 2 Describes the RAID Groups and the different ways

they store data.

Chapter 3 Describes installations for shared switched storage.

Chapter 4 Describes installations for unshared direct, and

shared-or-clustered direct, and shared switched

storage.

Chapter 5 Describes hardware components.

Chapter 6 Describes storage-system management utilities.

About Fibre Channel Storage Systems and Networks (SANs)

1-1

This chapter introduces Fibre Channel disk-array storage systems

and storage area networks (SANs). Major sections are

•Introducing EMC Fibre Channel Storage Systems........................1-2

•Fibre Channel Background...............................................................1-3

•Fibre Channel Storage Components................................................1-4

•About Switched Shared Storage and SANs (Storage Area

Networks).......................................................................................... 1-11

•About Unshared Storage.................................................................1-16

About Fibre Channel

Storage Systems and

Networks (SANs)

1-2

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

Introducing EMC Fibre Channel Storage Systems

EMC Fibre Channel disk-array storage systems provide terabytes of

disk storage capacity, high transfer rates, flexible configurations, and

highly available data at low cost.

A storage system package includes a host-bus adapter driver package

with hardware and software to connect with a server, storage

management software, Fibre Channel interconnect hardware, and

one or more storage systems.

Figure 1-1 Storage System Models

Fibre Channel Background

1-3

About Fibre Channel Storage Systems and Networks (SANs)

Fibre Channel Background

Fibre Channel is a high-performance serial protocol that allows

transmission of both network and I/O channel data. It is a low level

protocol, independent of data types, and supports such formats as

SCSI and IP.

The Fibre Channel standard supports several physical topologies,

including switched fabric point-to-point and arbitrated loop (FC-AL).

The topologies used by the Fibre Channel storage systems described

in this manual are switched fabric and FC-AL.

A switch fabric is a set of point-to-point connections between nodes,

the connection being made through one or more Fibre Channel

switches. Each node may have its own unique address, but the path

between nodes is governed by a switch. The nodes are connected by

optical cable.

A Fibre Channel arbitrated loop is a circuit consisting of nodes. Each

node has a unique address, called a Fibre Channel arbitrated loop

address. The nodes are connected by optical cables. An optical cable

can transmit data over great distances for connections that span

entire enterprises and can support remote disaster recovery systems.

Copper cable serves well for local connections; its length is limited to

30 meters (99 feet).

Each connected device in a switched fabric or arbitrated loop is a

server adapter (initiator) or a target (storage system). The switches

and hubs are not considered nodes.

Figure 1-2 Nodes - Initiator and Target

EMC1802

Server Adapter (initiator)

Connection

Storage System (target)

Node

Adapter

Node

1-4

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

Fibre Channel Storage Components

A Fibre Channel storage system has three main components:

•Server component (host-bus adapter driver package with adapter

and software)

•Interconnect components (cables based on Fibre Channel

standards, switches, and hubs)

•Storage components (storage system with storage processors —

SPs — and power supply and cooling hardware)

Server Component (Host-Bus Adapter Driver Package with Software)

The host-bus adapter driver package includes a host-bus adapter and

support software. The adapter is a printed-circuit board that slides

into an I/O slot in the server’s cabinet. It transfers data between

server memory and one or more disk-array storage systems over

Fibre Channel — as controlled by the support software (adapter

driver).

One or more servers can use a storage system. For high availability —

in event of an adapter failure — a server can have two adapters.

Depending on your server type, you may have a choice of adapters.

The adapter is designed for a specific host bus; for example, a PCI bus

or SBUS. Some adapter types support copper or optical cabling; some

support copper cabling only.

Interconnect Components

The interconnect components include the cables, Fibre Channel

switch (for shared storage), and Fibre Channel hub (for unshared

storage).

Cables Depending on your needs, you can choose copper or optical cables.

EMC1803

Adapter

Server

Fibre Channel Storage Components

1-5

About Fibre Channel Storage Systems and Networks (SANs)

The maximum length of copper cable is 30 meters (99 feet) between

nodes or hubs. The maximum length of optical cable between server

and hub or storage system is much greater, depending on the cable

type. For example, 62.5-micron multimode cable can span up to 500

meters (1,640 feet) while 9-micron single-mode cable can span up to

10 kilometers (6.2 miles). This ability to span great distances is a

major advantage of optical cable.

Some nodes have connections that require a specific type of cable:

copper or optical. Other nodes allow for the conversion from copper

to optical using a conversion device called a GigaBit Interface

Converter (GBIC) or Media Interface Adapter (MIA). In most cases, a

GBIC or MIA lets you substitute long-distance optical connections for

shorter copper connections.

With extenders, optical cable can span up to 40 km (25 miles). This

ability to span great distances is a major advantage of optical cable.

Details on cable lengths and rules appear later in this manual.

Fibre Channel Switches

A Fibre Channel switch, which is a requirement for shared storage (a

Storage Area Network, SAN) connects all the nodes cabled to it using

a fabric topology. A switch adds serviceability and scalability to any

installation; it allows on-line insertion and removal of any device on

the fabric and maintains integrity if any connected device stops

participating. A switch also provides host-to-storage-system access

control in a multiple-host shared-storage environment. A switch has

several advantages over a hub: it provides point-to-point connections

(as opposed to a hub’s loop that includes all nodes) and it offers

zoning to specify paths between nodes in the switch itself.

1-6

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

You can cascade switches (connect one switch port to another switch)

for additional port connections.

Figure 1-3 Switch and Hub Topologies Compared

Switch Zoning

Switch zoning defines paths between connected nodes. Each zone

encloses one or more adapters and one or more SPs. A switch can

have as many zones as it has ports. The current connection limits are

four SP ports to one adapter port (the SPs fan in to the adapter) and

15 adapters to one SP (the SPs fan out to the adapters). There are

several zone types, including the single-initiator type, which is the

recommended type.

In the following figure, Server 1 has access to one SP (SP A) in storage

systems 1 and 2; it has no access to any other SP.

witch uses discrete

onnections between

orts

SP SP

Server Server

Adapter

Storage systems

Adapter

Server

Adapter

Switch topology (point-to-point)

Hub uses

loop between

ports

Server Server

Adapter

Server

Adapter

Hub topology (loop)

o illustrate the comparison, this figure shows just one adapter per server and one switch or

hub. Normally, such installations include two adapters per server and two switches or hubs.

Fibre Channel Storage Components

1-7

About Fibre Channel Storage Systems and Networks (SANs)

Figure 1-4 A Switch Zone

If you do not define a zone in a switch, all adapter ports connected to

the switch can communicate with all SP ports connected to the

switch. However, access to an SP does not necessarily provide access

to the SP’s storage; access to storage is governed by the Storage

Groups you create (defined later).

Fibre Channel switches are available with 16 or 8 ports. They are

compact units that fit in 2 U (3.5 inches) for the 16-port or 1 U (1.75

inches) for the 8-port. They are available to fit into a rackmount

cabinet or as small deskside enclosures.

Figure 1-5 16-Port Switch, Back View

SP SP

Server

Adapter

Storage system 1

Adapter

SP SP SP

Zone

Switch

Storage system 2 Storage system 3

fabric

To illustrate switch zoning, this figure shows just one HBA per server and one

switch or hub. Normally, such installations will include two HBAs per server

and two switches or hubs.

EMC1807

Ports

1-8

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

If your servers and storage systems will be far apart, you can place

the switches closer to the servers or the storage systems, as

convenient.

A switch is technically a repeater, not a node, in a Fibre Channel loop.

However, it is bound by the same cabling distance rules as a node.

Fibre Channel Hubs A hub connects all the nodes cabled to it into a single logical loop. A

hub adds serviceability and scalability to any loop; it allows on-line

insertion and removal of any device on the loop and maintains loop

integrity if any connected device stops participating.

Fibre channel hubs are compact units that fit in 1 U (1.75 inches) of

storage space. They are available to fit into a rackmount cabinet or as

small deskside units.

Figure 1-6 Nine-Port Hub

If your servers and storage systems will be far apart, you can place

the hubs closer to the servers or the storage systems, as convenient.

The nine-pin port can connect to a server,

storage system, or another hub.

Fibre Channel Storage Components

1-9

About Fibre Channel Storage Systems and Networks (SANs)

Storage Component (Storage Systems, Storage Processors (SPs), and Other

Hardware)

EMC disk-array storage systems, with their storage processors,

power supplies, and cooling hardware form the storage component

of a Fibre Channel system. The controlling unit, a Disk-array

Processor Enclosure (DPE) looks like the following figure.

Figure 1-7 Disk-Array Processor Enclosure (DPE)

DPE hardware details appear in a later chapter.

EMC1808

Disk

modules

1-10

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

Types of Storage System Installations

You can use a storage systems in any of several types of installation:

•Unshared direct with one server is the simplest and least costly;

•Shared-or-clustered direct lets two clustered servers share

storage resources with high availability (FC4500 storage systems;

and

•Shared switched, with one or two switch fabrics, lets two to 15

servers share the resources of several storage systems in a Storage

Area Network (SAN) Shared switched installations are available

in a high-availability (HA) version, with two HBAs per server,

with two switches, or with one HBA per server and one switch.

Figure 1-8 Types of Storage System Installation

Storage systems for any shared installation require EMC Access

Logix™ software to control server access to the storage system LUNs.

The Shared-or-clustered direct installation may be either shared (that

is, use Access Logix to control LUN access) or clustered (without

Access Logix, using cluster software to control LUN access),

depending on the hardware model.

Disk-array storage systems

Server

Adapter

Server

Adapter

Server

Adapter

Server

Adapter

Server

Adapter

Server

Adapter

Shared-or-Clustered Direct

(two servers)

Switch fabric Switch fabric

Shared Switched

(multiple servers)

Unshared Direct

(one or two servers)

Path 1

Path 2

About Switched Shared Storage and SANs (Storage Area Networks)

1-11

About Fibre Channel Storage Systems and Networks (SANs)

About Switched Shared Storage and SANs (Storage Area

Networks)

This section explains the features that let multiple servers share

disk-array storage systems on a SAN (storage area network).

A SAN is a collection of storage devices connected to servers via Fibre

Channel switches to provide a central location for disk storage.

Centralizing disk storage among multiple servers has many

advantages, including

•highly available data

•flexible association between servers and storage capacity

•centralized management for fast, effective response to users’ data

storage needs

•easier file backup and recovery

An EMC SAN is based on shared storage; that is, the SAN requires

the Access Logix option to provides flexible access control to storage

system LUNs.

Figure 1-9 Components of a SAN

Fibre Channel switches can control data access to storage systems

through the use of switch zoning. With zoning, an administrator can

specify groups (called zones) of Fibre Channel devices (such as

host-bus adapters, specified by worldwide name), and SPs between

which the switch will allow communication.

SP A

Server Server

SP B

Storage systems

Switch fabric

Adapter

Server

SP A SP B

Switch fabric

Path 1

Path 2

1-12

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

However, switch zoning cannot selectively control data access to

LUNs in a storage system, because each SP appears as a single Fibre

Channel device to the switch. So switch zoning can prevent or allow

communication with an SP, but not with specific disks or LUNs

attached to an SP. For access control with LUNs, a different solution is

required: Storage Groups.

Storage Groups A Storage Group is one or more LUNs (logical units) within a storage

system that is reserved for one or more servers and is inaccessible to

other servers. Storage Groups are the central component of shared

storage; storage systems that are unshared do not use Storage

Groups.

When you configure shared storage, you specify servers and the

Storage Group(s) each server can read from and/or write to. The Base

Software firmware running in each storage system enforces the

server-to-Storage Group permissions.

A Storage Group can be accessed by more than one server if all the

servers run cluster software. The cluster software enforces orderly

access to the shared Storage Group LUNs.

The following figure shows a simple shared storage configuration

consisting of one storage system with two Storage Groups. One

Storage Group serves a cluster of two servers running the same

operating system, and the other Storage Group serves a UNIX

database server. Each server is configured with two independent

paths to its data, including separate host-bus adapters, switches, and

SPs, so there is no single point of failure for access to its data.

About Switched Shared Storage and SANs (Storage Area Networks)

1-13

About Fibre Channel Storage Systems and Networks (SANs)

Figure 1-10 Sample SAN Configuration

Access Control with Shared Storage

Access control permits or restricts a server’s access to shared storage.

There are two kinds of access control:

•Configuration access control

•Data access control

Configuration access control lets you restrict the servers through

which a user can send configuration commands to an attached

storage system.

Data access control is provided by Storage Groups. During storage

system configuration, using a management utility, the system

administrator associates a server with one or more LUNs.

Each server sees its Storage Group as if it were an entire storage

system, and never sees the other LUNs on the storage system.

Therefore, it cannot access or modify data on LUNs that are not part

of its Storage Group. However, you can define a Storage Group to be

accessible by more than one server, if, as shown above, the servers

run cluster software.

Highly available cluster

SP A

LUN

Cluster

Storage Group

Database Server

Storage Group

Physical storage

systems with up to

100 disks per storage

system

Switch fabric

File Server Mail Server Database Server

Adapter

Operating

system A

Adapter

Operating

system A

Adapter

Operating

system B

SP B

Switch fabric

Path 1

Path 2

1-14

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

The following figure shows both data access control (Storage Groups)

and configuration access control. Each server has exclusive read and

write access to its designated Storage Group. Of the four servers

connected to the SAN, only the Admin server can send configuration

commands to the storage system.

Figure 1-11 Data and Configuration Access Control with Shared Storage

Admin Storage Group LUN

LUN

Inventory Storage Group

E-mail and Web server

Storage Group

SP B

Highly available cluster

Data access by adapters 01, 02

Data access by adapters 03, 04

Data access by

adapters 05, 06, 07, 08

Shared

Dedicated

Configuation access, by

adapters 01and 02

(Admin server only)

Switch fabric

SP A

Web server

Inventory server E-mail server

Admin server

Adapter

03 04

Operating

system A

Adapter

01 02

Operating

system A

Adapter

05 06

Operating

system B

Adapter

07 08

Operating

system B

Switch fabric

About Switched Shared Storage and SANs (Storage Area Networks)

1-15

About Fibre Channel Storage Systems and Networks (SANs)

Storage System Hardware for Shared Storage

For shared storage, you need a Disk-array Processor Enclosure (DPE)

storage system.

A DPE is a 10-slot enclosure with hardware RAID features provided

by one or two storage processors (SPs). For shared storage, two SPs

are required. In addition to its own disks, a DPE can support up to

nine 10-slot Disk Array Enclosures (DAEs) for a total of 100 disks.

Figure 1-12 Storage System with a DPE and Three DAEs

EMC1741

DPE

DAE

Standby power

supply (SPS)

1-16

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

About Unshared Storage

Unshared storage systems are less costly and less complex than

shared storage systems. They offer many shared storage system

features; for example, you can use multiple unshared storage systems

with multiple servers. However, with multiple servers, unshared

storage offers less flexibility and security than shared storage, since

any user with write access to a privileged server’s files can enable

access to any storage system.

Storage System Hardware for Unshared Storage

For unshared storage, there are four types of storage system, each

using the FC-AL protocol. Each type is available in a rackmount or

deskside (office) version.

•Disk-array Processor Enclosure (DPE) storage systems. A DPE is

a 10-slot enclosure with hardware RAID features provided by one

or two storage processors (SPs). In addition to its own disks, a

DPE can support up to 110 additional disks in 10-slot Disk Array

Enclosures (DAEs) for a total of 120 disks. This is the same type of

storage system used for shared storage, but it has a different SP

and different Core Software.

•Intelligent Disk Array Enclosure (iDAE). An iDAE, like a DPE,

has SPs and thus all the features of a DPE, but is thinner and has a

limit of 30 disks.

•Disk Array Enclosure (DAE). A DAE does not have SPs. A DAE

can connect to a DPE or an iDAE, or you can use it without SPs. A

DAE used without an SP does not inherently include RAID, but

can operate as a RAID device using software running on the

server system. Such a DAE is also known as Just a Box of Disks, or

JBOD.

About Unshared Storage

1-17

About Fibre Channel Storage Systems and Networks (SANs)

Figure 1-13 Storage System Hardware for Unshared Storage

What Next? For information about RAID types and RAID tradeoffs, continue to

the next chapter. To plan LUNs and file systems for shared storage,

skip to Chapter 3; or for unshared storage, Chapter 4. For details on

the storage-system hardware — shared and unshared — skip to

Chapter 5. For storage-system management utilities, skip to

Chapter 6.

Deskside DPE with DAE Rackmount DPE, one enclosure,

supports up to 9 DAEs

Disk-array processor enclosure (DPE)

Intelligent disk-array enclosure (iDAE)

30-slot deskside Rackmount10-slot deskside

1-18

EMC Fibre Channel Storage-System Configuration Planning

About Fibre Channel Storage Systems and Networks (SANs)

RAID Types and Tradeoffs

2-1

This chapter explains RAID types you can choose for your storage

system LUNs. If you already know about RAID types and know

which ones you want, you can skip this background information and

skip to Chapter 5. Topics are

•Introducing RAID ..............................................................................2-2

•RAID Types.........................................................................................2-4

•RAID Benefits and Tradeoffs..........................................................2-12

•Guidelines for RAID Types.............................................................2-17

•Sample Applications for RAID Types...........................................2-19

This chapter applies primarily to storage systems with storage processors

(SPs). For a storage system without SPs (a DAE-only or JBOD system), RAID

types are limited by the RAID software you run on the server. The RAID

terms and definitions used here conform to generally accepted standards.

RAID Types and

Tradeoffs

2-2

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

Introducing RAID

The storage system uses RAID (redundant array of independent

disks) technology. RAID technology groups separate disks into one

logical unit (LUN) to improve reliability and/or performance.

The storage system supports five RAID levels and two other disk

configurations, the individual unit and the hot spare (global spare).

You group the disks into one RAID Group by binding them using a

storage-system management utility.

Four of the RAID types use disk striping and two use mirroring.

Disk Striping Using disk stripes, the storage-system hardware can read from and

write to multiple disks simultaneously and independently. By

allowing several read/write heads to work on the same task at once,

disk striping can enhance performance. The amount of information

read from or written to each disk makes up the stripe element size.

The stripe size is the stripe element size multiplied by the number of

disks in a group. For example, assume a stripe element size of 128

sectors (the default) and a five-disk group. The group has five disks,

so you would multiply five by the stripe element size of 128 to yield a

stripe size of 640 sectors.

The storage system uses disk striping with most RAID types.

Mirroring Mirroring maintains a second (and optionally through software, a

third) copy of a logical disk image that provides continuous access if

the original image becomes inaccessible. The system and user

applications continue running on the good image without

interruption. There are two kinds of mirroring: hardware mirroring,

in which the SP synchronizes the disk images; and software

mirroring, in which the operating system synchronizes the images.

Software mirroring consumes server resources, since the operating

system must mirror the images, and has no offsetting advantages; we

mention it here only for historical completeness.

With a storage system, you can create a hardware mirror by binding

disks as a RAID 1 mirrored pair or a RAID 1/0 Group (a mirrored

RAID 0 Group); the hardware will then mirror the disks

automatically.

Introducing RAID

2-3

RAID Types and Tradeoffs

RAID Groups and

LUNs Some RAID types let you create multiple LUNs on one RAID Group.

You can then allot each LUN to a different user, server, or application.

For example, a five-disk RAID 5 Group that uses 36-Gbyte disks

offers 144 Gbytes of space. You could bind three LUNs, say with 24,

60, and 60 Gbytes of storage capacity, for temporary, mail, and

customer files.

One disadvantage of multiple LUNs on a RAID Group is that I/O to

each LUN may affect I/O to the others in the group; that is, if traffic

to one LUN is very heavy, I/O performance with other LUNs may

degrade. The main advantage of multiple LUNs per RAID Group is

the ability to divide the enormous amount of disk space provided by

RAID Groups on newer, high-capacity disks.

Figure 2-1 Multiple LUNs in a RAID Group

EMC1814

RAID Group

Disk Disk Disk Disk Disk

LUN 0

temp

LUN 1

mail

LUN 2

customers

LUN 0

temp

LUN 1

mail

LUN 2

customers

LUN 0

temp

LUN 1

mail

LUN 2

customers

LUN 0

temp

LUN 1

mail

LUN 2

customers

LUN 0

temp

LUN 1

mail

LUN 2

customers

2-4

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

RAID Types

You can choose from the following RAID types: RAID 5, RAID 3,

RAID 1, RAID 0, RAID 1/0, individual disk unit, and hot spare.

RAID 5 Group (Individual Access Array)

A RAID 5 Group usually consists of five disks (but can have three to

sixteen). A RAID 5 Group uses disk striping. With a RAID 5 Group on

a full-fibre storage system, you can create up to 32 RAID 5 LUNs to

apportion disk space to different users, servers, and applications.

The storage system writes parity information that lets the group

continue operating if a disk fails. When you replace the failed disk,

the SP rebuilds the group using the information stored on the

working disks. Performance is degraded while the SP rebuilds the

group. However, the storage system continues to function and gives

users access to all data, including data stored on the failed disk.

The following figure shows user and parity data with the default

stripe element size of 128 sectors (65,536 bytes) in a five-disk RAID 5

Group. The stripe size comprises all stripe elements. Notice that the

disk block addresses in the stripe proceed sequentially from the first

disk to the second, third, and fourth, then back to the first, and so on.

RAID Types

2-5

RAID Types and Tradeoffs

Figure 2-2 RAID 5 Group

RAID 5 Groups offer excellent read performance and good write

performance. Write performance benefits greatly from

storage-system caching.

RAID 3 Group (Parallel Access Array)

A RAID 3 Group consists of five or more disks. The hardware always

reads from or writes to all the disks. A RAID 3 Group uses disk

striping. To maintain the RAID 3 performance, you can create only

one LUN per RAID 3 Group.

The storage system writes parity information that lets the group

continue operating if a disk fails. When you replace the failed disk,

the SP rebuilds the group using the information stored on the

working disks. Performance is degraded while the SP rebuilds the

group. However, the storage system continues to function and gives

users access to all data, including data stored on the failed disk.

EMC1815

Second disk

128-255 640-767 1152-1279 Parity 2048-2175

Parity

Third disk

256-383 768-895 1664-1791 2176-2303

Parity Fourth disk

384-511 1280-1407 1792-1919 2304-2431

Parity Fifth disk

896-1023 1408-1535 1920-2047 2432-2559

Stripe

element

size

Stripe

size

First disk

512-639 1024-11511536-1663 Parity

0-127

Blocks

User data

Parity data

…

2-6

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

The following figure shows user and parity data with a data block

size of 2 Kbytes in a RAID 3 Group. Notice that the byte addresses

proceed from the first disk to the second, third, and fourth, then the

first, and so on.

Figure 2-3 RAID 3 Group

RAID 3 differs from RAID 5 in several important ways. First, in a

RAID 3 Group the hardware processes disk requests serially; whereas

in a RAID 5 Group the hardware can interleave disk requests. Second,

with a RAID 3 Group, the parity information is stored on one disk;

with a RAID 5 Group, it is stored on all disks. Finally, with a RAID 3

Group, the I/O occurs in small units (one sector) to each disk. A

RAID 3 Group works well for single-task applications that use I/Os

of blocks larger than 64 Kbytes.

Each RAID 3 Group requires some dedicated SP memory (6 Mbytes

recommended per group). This memory is allocated when you create

the group and becomes unavailable for storage-system caching. For

top performance, we suggest that you do not use RAID 3 Groups

with RAID 5, RAID 1/0, or RAID 0 Groups, since SP processing

power and memory are best devoted to the RAID 3 Groups. RAID 1

mirrored pairs and individual units require less SP processing power,

and therefore work well with RAID 3 Groups.

EMC1816

Second disk

Third disk

Fourth disk

Fifth disk

Stripe

element

size

Stripe

size

…

First disk

User data

Parity data

2048-2559 4096-4607 6144-6655 8192-8603

0-511

512-1023 2560-3071 4608-5119 6656-7167 8604-9115

5120-56311024-1535 3072-3583 7168-7679 9116-9627

3584-40951536-2047 5632-6143 7680-81919628-10139

Parity Parity Parity Parity Parity

Data block

Bytes

RAID Types

2-7

RAID Types and Tradeoffs

For each write to a RAID 3 Group, the storage system

1. Calculates the parity data.

2. Writes the new user and parity data.

RAID 1 Mirrored Pair A RAID 1 Group consists of two disks that are mirrored

automatically by the storage-system hardware.

RAID 1 hardware mirroring within the storage system is not the same

as software mirroring or hardware mirroring for other kinds of disks.

Functionally, the difference is that you cannot manually stop

mirroring on a RAID 1 mirrored pair, and then access one of the

images independently. If you want to use one of the disks in such a

mirror separately, you must unbind the mirror (losing all data on it),

rebind the disk in as the type you want, and software format the

newly bound LUN.

With a storage system, RAID 1 hardware mirroring has the following

advantages:

•automatic operation (you do not have to issue commands to

initiate it)

•physical duplication of images

•a rebuild period that you can select during which the SP recreates

the second image after a failure

With a RAID 1 mirrored pair, the storage system writes the same data

to both disks, as follows.

Figure 2-4 RAID 1 Mirrored Pair

EMC1817

Second disk

…

First disk

User data

2-8

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

RAID 0 Group (Nonredundant Array)

A RAID 0 Group consists of three to a maximum of sixteen disks. A

RAID 0 Group uses disk striping, in which the hardware writes to or

reads from multiple disks simultaneously. In a full-fibre storage

system, you can create up to 32 LUNs per RAID Group.

Unlike the other RAID levels, with RAID 0 the hardware does not

maintain parity information on any disk; this type of group has no

inherent data redundancy. RAID 0 offers enhanced performance

through simultaneous I/O to different disks.

If the operating system supports software mirroring, you can use

software mirroring with the RAID 0 Group to provide high

availability. A desirable alternative to RAID 0 is RAID 1/0.

RAID 1/0 Group (Mirrored RAID 0 Group)

A RAID 1/0 Group consists of four, six, eight, ten, twelve, fourteen,

or sixteen disks. These disks make up two mirror images, with each

image including two to eight disks. The hardware automatically

mirrors the disks. A RAID 1/0 Group uses disk striping. It combines

the speed advantage of RAID 0 with the redundancy advantage of

mirroring. With a RAID 1/0 Group on a full-fibre storage system, you

can create up to 32 RAID 5 LUNs to apportion disk space to different

users, servers, and applications.

The following figure shows the distribution of user data with the

default stripe element size of 128 sectors (65,536 bytes) in a six-disk

RAID 1/0 Group. Notice that the disk block addresses in the stripe

proceed sequentially from the first mirrored disks (first and fourth

disks) to the second mirrored disks (second and fifth disks), to the

third mirrored disks (third and sixth disks), and then from the first

mirrored disks, and so on.

RAID Types

2-9

RAID Types and Tradeoffs

Figure 2-5 RAID 1/0 Group (Mirrored RAID 0 Group)

A RAID 1/0 Group can survive the failure of multiple disks,

providing that one disk in each image pair survives.

Individual Disk Unit An individual disk unit is a disk bound to be independent of any

other disk in the cabinet. An individual unit has no inherent high

availability, but you can make it highly available by using software

mirroring with another individual unit. You can create one LUN per

individual disk unit. If you want to apportion the disk space, you can

do so using partitions, file systems, or user directories.

Hot Spare A hot spare is a dedicated replacement disk on which users cannot

store information. A hot spare is global: if any disk in a RAID 5

Group, RAID 3 Group, RAID 1 mirrored pair, or RAID 1/0 Group

fails, the SP automatically rebuilds the failed disk’s structure on the

hot spare. When the SP finishes rebuilding, the disk group functions

as usual, using the hot spare instead of the failed disk. When you

EMC1818

Stripe

element

size

Stripe

size …

…

User data

First disk of primary image

Second disk of primary image

Third disk of primary image

Third disk of secondary image

First disk of secondary image

Second disk of secondary image

512-639128-255 1664-17911280-1407896-1023

1536-16631152-1279768-895

…

512-639

1024-1151

1536-16630-127

128-255

640-767

1152-1279

256-383

768-895

1664-1791

384-511

1280-1407

1792-1919

896-1023

1408-1535

Stripe

Blocks

0-127 384-511

2-10

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

replace the failed disk, the SP copies the data from the former hot

spare onto the replacement disk.

When the copy is done, the disk group consists of disks in the original

slots, and the SP automatically frees the hot spare to serve as a hot

spare again. A hot spare is most useful when you need the highest

data availability. It eliminates the time and effort needed for someone

to notice that a disk has failed, find a suitable replacement disk, and

insert the disk.

When you plan to use a hot spare, make sure the disk has the capacity to

serve in any RAID Group in the storage-system chassis. A RAID Group

cannot use a hot spare that is smaller than a failed disk in the group.

You can have one or more hot spares per storage-system chassis. You

can make any disk in the chassis a hot spare, except for a disk that

serves for Core Software storage or the write cache vault. That is, a

hot spare can be any of the following disks:

An example of hot spare usage for a deskside DPE storage system

follows.

DPE or iDAE system without write caching: disks 3-119

DPE system with write caching: disks 9-119

iDAE system with write caching: disks 5-29

30-slot SCSI-disk system: disks A1-E1, A2-E2,

B3-E3, A4-E4

RAID Types

2-11

RAID Types and Tradeoffs

Figure 2-6 How a Hot Spare Works

Hot spare

1. RAID 5 group consists of disk modules 0-4; RAID 1 mirrored pair is

modules 5 and 6; hot spare is module 9.

2. Disk module 3 fails.

3. RAID 5 group becomes modules 0, 1, 2, 9, and 4; now no hot spare is

available.

4. System operator replaces failed module 3 with a functional module.

5. RAID 5 group once again is 0-4 and hot spare is 9.

2-12

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

RAID Benefits and Tradeoffs

This section reviews RAID types and explains their benefits and

tradeoffs. You can create seven types of LUN:

•RAID 5 Group (individual access array)

•RAID 3 Group (parallel access array)

•RAID 1 mirrored pair

•RAID 1/0 Group (mirrored RAID 0 Group); a RAID 0 Group

mirrored by the storage-system hardware

•RAID 0 Group (nonredundant individual access array); no

inherent high-availability features, but can be software mirrored

if the operating system supports mirroring

•Individual unit; no inherent high-availability features but can be

software mirrored, if the operating system supports mirroring

•Hot spare; serves only as an automatic replacement for any disk

in a RAID type other than 0; does not store data during normal

system operations

Plan the disk unit configurations carefully. After a disk has been bound into a

LUN, you cannot change the RAID type of that LUN without unbinding it,

and this means losing all data on it.

The following table compares the read and write performance,

tolerance for disk failure, and relative cost per megabyte (Mbyte) of

the RAID types. Figures shown are theoretical maximums.

RAID Benefits and Tradeoffs

2-13

RAID Types and Tradeoffs

Table 2-1 Performance, Availability, and Cost of RAID Types (Individual Unit = 1.0)

Performance RAID 5, with individual access, provides high read throughput for

small requests (blocks of 2 to 8 Kbytes) by allowing simultaneous

reads from each disk in the group. RAID 5 write throughput is

limited by the need to perform four I/Os per request (I/Os to read

and write data and parity information). However, write caching

improves RAID 5 write performance.

RAID 3, with parallel access, provides high throughput for

sequential, large block-size requests (blocks of more than 64 Kbytes).

With RAID 3, the system accesses all five disks in each request but

need not read data and parity before writing – advantageous for large

requests but not for small ones. RAID 3 employs SP memory without

caching, which means you do not need the second SP and BBU that

caching requires.

Generally, the performance of a RAID 3 Group increases as the size of

the I/O request increases. Read performance increases rapidly with

read requests up to 1Mbyte. Write performance increases greatly for

sequential write requests that are greater than 256 Kbytes. For

applications issuing very large I/O requests, a RAID 3 LUN provides

significantly better write performance than a RAID 5 LUN.

Disk configuration

Relative read

performance

without cache

Relative write

performance

without cache

Relative

cost per

Mbyte

RAID 5 Group with

fivedisks

Up to 5 with five disks

(for small I/O requests, 2

to 8 Kbytes)

Up to 1.25 with five disks

(for small I/O requests, 2 to

8 Kbytes)

1.25

RAID 3 Group with

fivedisks

Up to 4 (for large I/O

requests)

Up to 4 (for large I/O

requests)

1.25

RAID 1 mirrored pair Up to 2 Up to 1 2

RAID 1/0 Group with

10 disks

Up to 10 Up to 5

Individual unit 1 1 1

Notes: These performance numbers are not based on storage-system caching. With caching,

the performance numbers for RAID 5 writes improve significantly.

Performance multipliers vary with load on server and storage system.

2-14

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

We do not recommend using RAID 3 in the same storage-system

chassis with RAID 5 or RAID 1/0.

A RAID 1 mirrored pair has its disks locked in synchronization, but

the SP can read data from the disk whose read/write heads are closer

to it. Therefore, RAID 1 read performance can be twice that of an

individual disk while write performance remains the same as that of

an individual disk.

A RAID 0 Group (nonredundant individual access array) or RAID

1/0 Group (mirrored RAID 0 Group) can have as many I/O

operations occurring simultaneously as there are disks in the group.

Since RAID 1/0 locks pairs of RAID 0 disks the same way as RAID 1

does, the performance of RAID 1/0 equals the number of disk pairs

times the RAID 1 performance number. If you want high throughput

for a specific LUN, use a RAID 1/0 or RAID 0 Group. A RAID 1/0

Group requires at least six disks; a RAID 0 Group, at least three disks.

An individual unit needs only one I/O operation per read or write

operation.

RAID types 5, 1, 1/0, and 0 allow multiple LUNs per RAID Group. If

you create multiple LUNs on a RAID Group, the LUNs share the

RAID Group disks, and the I/O demands of each LUN affect the I/O

service time to the other LUNs. For best performance, you may want

to use one LUN per RAID Group.

Storage Flexibility Certain RAID Group types — RAID 5, RAID 1, RAID 1/0, and RAID

0 — let you create up to 32 LUNs in each group. This adds flexibility,

particularly with large disks, since it lets you apportion LUNs of

various sizes to different servers, applications, and users. Conversely,

with RAID 3, there can be only one LUN per RAID Group, and the

group must include five or nine disks — a sizable block of storage to

devote to one server, application, or user. However, the nature of

RAID 3 makes it ideal for that single-threaded type of application.

Data Availability and Disk Space Usage

If data availability is critical and you cannot afford to wait hours to

replace a disk, rebind it, make it accessible to the operating system,

and load its information from backup, then use a redundant RAID

Group: RAID 5, RAID 3, RAID 1 mirrored pair, or RAID 1/0. Or bind

a RAID 0 Group or individual disk unit that you will later mirror

with software mirroring. If data availability is not critical, or disk

RAID Benefits and Tradeoffs

2-15

RAID Types and Tradeoffs

space usage is critical, bind an individual unit or RAID 0 Group

without software mirroring.

A RAID 1 mirrored pair or RAID 1/0 Group provides very high data

availability. They are more expensive than RAID 5 or RAID 3 Groups,

since only 50 percent of the total disk capacity is available for user

data, as shown on page 2-13.

A RAID 5 or RAID 3 Group provides high data availability, but

requires more disks than a mirrored pair. In a RAID 5 or RAID 3

Group of five disks, 80 percent of the disk space is available for user

data. So RAID 5 and RAID 3 Groups use disk space much more

efficiently than a mirrored pair. A RAID 5 or RAID 3 Group is usually

more suitable than a RAID 1 mirrored pair for applications where

high data availability, good performance, and efficient disk space

usage are all of relatively equal importance.

2-16

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

Figure 2-7 Disk Space Usage in the RAID Configurations

A RAID 0 Group (nonredundant individual access array) provides all

its disk space for user files, but does not provide any high availability

features.

A RAID 1/0 Group provides the best combination of performance

and availability, at the highest cost per Mbyte of disk space.

An individual unit, like a RAID 0 Group, provides no

high-availability features. All its disk space is available for user data,

as shown in the figure above.

EMC1820

RAID 5 Group RAID 3 Group

2nd disk

user and parity data

2nd disk

user data

3rd disk

user and parity data

3rd disk

user data

4th disk

user and parity data

4th disk

user data

1st disk

user and parity data

1st disk

user data

5th disk

user and parity data

5th disk

parity data

80% user data

20% parity data

RAID 1/0 Group

2nd disk

user data

3rd disk

user data

4th disk

user data

6th disk

user data

1st disk

user data

5th disk

user data

50% user data

50% redundant data

RAID 0 Group

(nonredundant array)

2nd disk

user data

3rd disk

user data

1st disk

user data

100% user data

2nd disk

user data

1st disk

user data

Disk Mirror (RAID 1 mirrored pair)

50% user data

50% redundant data

User data

Individual Disk Unit

100% user dataReserved

Hot Spare

No user data

Guidelines for RAID Types

2-17

RAID Types and Tradeoffs

Guidelines for RAID Types

To decide when to use a RAID 5 Group, RAID 3 Group, mirror (that

is, a RAID 1 mirrored pair or RAID 1/0 Group), a RAID 0 Group,

individual disk unit, or hot spare, you need to weigh these factors:

•Importance of data availability

•Importance of performance

•Amount of data stored

•Cost of disk space

The following guidelines will help you decide on RAID types.

Use a RAID 5 Group (individual access array) for applications

where

•Data availability is very important

•Large volumes of data will be stored

•Multitask applications use I/O transfers of different sizes

•Good read and moderate write performance are important (write

caching can improve (RAID 5 write performance)

•You want the flexibility of multiple LUNs per RAID Group

Use a RAID 3 Group (parallel access array) for applications where

•Data availability is very important

•Large volumes of data will be stored

•A single-task application uses large I/O transfers (more than 64

Kbytes). The operating system must allow transfers aligned to

start at disk addresses that are multiples of 2 Kbytes from the start

of the LUN.

Use a RAID 1 mirrored pair for applications where

•Data availability is very important

•Speed of write access is important and write activity is heavy

Use a RAID 1/0 Group (mirrored nonredundant array) for

applications where

•Data availability is critically important

•Overall performance is very important

2-18

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

Use a RAID 0 Group (nonredundant individual access array) for

applications where

•High availability is not important

•Overall performance is very important

Use an individual unit for applications where

•High availability is not important

•Speed of write access is somewhat important

Use a hot spare where

•In any RAID 5, RAID 3, RAID 1/0 or RAID 1 Group, high

availability is so important that you want to regain data

redundancy quickly without human intervention if any disk in

the Group fails

•Minimizing the degraded performance caused by disk failure in a

RAID 5 or RAID 3 Group is important

Sample Applications for RAID Types

2-19

RAID Types and Tradeoffs

Sample Applications for RAID Types

This section describes some types of applications in which you would

want to use a RAID 5 Group, RAID 3 Group, RAID 1 mirrored pair,

RAID 0 Group (nonredundant array), RAID 1/0 Group, or individual

unit.

RAID 5 Group (individual access array) — Useful as a database

repository or a database server that uses a normal or low percentage

of write operations (writes are 33 percent or less of all I/O

operations). Use a RAID 5 Group where multitask applications

perform I/O transfers of different sizes. Write caching can

significantly enhance the write performance of a RAID 5 Group.

For example, a RAID 5 Group is suitable for multitasking

applications that require a large history database with a high read

rate, such as a database of legal cases, medical records, or census

information. A RAID 5 Group also works well with transaction

processing applications, such as an airline reservations system, where

users typically read the information about several available flights

before making a reservation, which requires a write operation. You

could also use a RAID 5 Group in a retail environment, such as a

supermarket, to hold the price information accessed by the

point-of-sale terminals. Even though the price information may be

updated daily, requiring many write operations, it is read many more

times during the day.

RAID 3 Group — A RAID 3 Group (parallel access array) works well

with a single-task application that uses large I/O transfers (more than

64 Kbytes), aligned to start at a disk address that is a multiple of 2

Kbytes from the beginning of the logical disk. RAID 3 Groups can use

SP memory to great advantage without the second SP and battery

backup unit required for storage-system caching.

You might use a RAID 3 Group for a single-task application that does

large I/O transfers, like a weather tracking system, geologic charting

application, medical imaging system, or video storage application.

RAID 1 mirrored pair — A RAID 1 mirrored pair is useful for

logging or record-keeping applications because it requires fewer

disks than a RAID 0 Group (nonredundant array) and provides high

availability and fast write access. Or you could use it to store daily

updates to a database that resides on a RAID 5 Group, and then,

during off-peak hours, copy the updates to the database on the

RAID 5 Group.

2-20

EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

RAID 0 Group (nonredundant individual access array) — Use a

RAID 0 Group where the best overall performance is important. In

terms of high availability, a RAID 0 Group is less available than an

individual unit. A RAID 0 Group (like a RAID 5 Group) requires a

minimum of three disks. A RAID 0 Group serves well for an

application that uses short-term data to which users need quick

access.

RAID 1/0 Group (mirrored RAID 0 Group) — A RAID 1/0 Group

provides the best balance of performance and availability. You can

use it very effectively for any of the RAID 5 applications. A RAID 1/0

Group requires a minimum of four disks.

Individual unit — An individual unit is useful for print spooling,

user file exchange areas, or other such applications, where high

availability is not important or where the information stored is easily

restorable from backup.

The performance of an individual unit is slightly less than a standard

disk not in an storage system. The slight degradation results from SP

overhead.

Hot spare — A hot spare provides no data storage but enhances the

availability of each RAID 5, RAID 3, RAID 1, and RAID 1/0 Group in

a storage system. Use a hot spare where you must regain high

availability quickly without human intervention if any disk in such a

RAID Group fails. A hot spare also minimizes the period of degraded

performance after a RAID 5 or RAID 3 disk fails.

What Next? This chapter explained RAID Group types and tradeoffs. To plan

LUNs and file systems for shared storage, continue to Chapter 3; or

for unshared storage, skip to Chapter 4. For details on storage-

system hardware — shared and unshared — skip to Chapter 5.

For storage-system management utilities, skip to Chapter 6.

Planning File Systems and LUNs with Shared Switched Storage

3-1

This chapter shows a sample RAID, LUN, and Storage Group

configuration with shared storage, and then provides worksheets for

planning your own shared storage installation. Topics are

•Dual Paths to LUNs...........................................................................3-2

•Sample Shared Switched Installation..............................................3-3

•Planning Applications, LUNs, and Storage Groups.....................3-6

Planning File Systems

and LUNs with Shared

Switched Storage

3-2

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

Dual Paths to LUNs

A shared storage system includes two or more servers, one or two

Fibre Channel switches, and one or more storage systems, each with

two SPs and Access Logix software.

With shared storage, there are two paths to each LUN in the storage

system. The storage-system software, using optional software called

Application Transparent Failover (ATF), can automatically switch to

the other path if a device (such as a host-bus adapter or cable) fails.

With unshared storage, if the server has two adapters and the storage

system has two SPs, ATF software is available as an option. With two

adapters and two SPs, ATF can perform the same function as with

shared systems: automatically switch to the other path if a device

(such as host bus adapter or cable) fails.

Sample Shared Switched Installation

3-3

Planning File Systems and LUNs with Shared Switched Storage

Sample Shared Switched Installation

The following figure shows a sample shared switched

(high-availability) storage system connected to three servers: two

servers in a cluster and one server running a database management

program.

Figure 3-1 Sample Shared Switched High Availability installation

SP B

SP A

Cluster

Storage Group

Database Server

Storage Group

File Server (FS) Mail Server(MS) Database Server(DS)

Switch fabric

Adapter

Operating

system A

Adapter

Operating

system A

Adapter

Operating

system B

1_0-1_9

2_0-2_9

0_0-0_9

3_0-3_9

4_0-4_9

Path 2

Path 1

MS R5

ISP B mail

MS R5

ISP A mail

DS R5 (6

disks) Dbase1

DS R1

LogD1

FS R5

Files A FS R5

Files B

DS R5

Dbase2

DS R5

Users

MS R5

Users MS R5

Specs

Private storage

Highly available cluster

Disk IDs

Switch fabric

Spare

3-4

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

The storage-system disk IDs and server Storage Group LUNs are as

follows.

With 36-Megabyte disks, the LUN storage capacities and drive names

are as follows.

File Server — 288 Gbytes on two LUNs

Unit U on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for file storage.

Unit V on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for file storage.

Clustered System LUNs Database Server LUNs (DS) - SP A

File Server LUNs (FS) - SP B Mail Server LUNs (MS) - SP A

Disk IDs RAID type, storage type

4_0-4_4 RAID 5, Files A

4_5-4_9 RAID 5, Files B

Disk IDs RAID type, storage type

2_0-2_4 RAID 5, ISP A mail

2_5-2_9 RAID 5, ISP B mail

3_0-3_4 RAID 5, Users

3_5-3_9 RAID 5, Specs

Disk IDs RAID type, storage type

0_0, 0_ 1 RAID 1, Log file for

database Dbase1

0_4-0_9 RAID 5 (6 disks), Dbase1

1_0-1_4 RAID 5, Users

1_5-1_9 RAID 5, Dbase2

6_0, 6_1 – Hot spare (automatically replaces a failed disk in any server’s LUN)

FS R5

FilesA

FS R5

FilesB

Sample Shared Switched Installation

3-5

Planning File Systems and LUNs with Shared Switched Storage

Mail Server — 576 Gbytes on four LUNs

Unit O on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for the mail delivered via ISP A.

Unit P on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for the mail delivered via ISP B.

Unit Q on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for user directories and files.

Unit R on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for specifications.

Database Server — 416 Gbytes on four LUNs

Unit users on five disks bound as a RAID 5 Group for

144 Gbytes of storage; for user directories.

Unit dbase2 on five disks bound as a RAID 5 Group

for 144 Gbytes of storage; for the second database system.

Unit logfiles on two disks bound as a RAID 1 mirrored

pair for 36 Gbytes of storage; for the database log files.

Unit dbase on six disks bound as a RAID 5 Group for

180 Gbytes of storage; for the primary database system.

MS R5

ISP mail

MS R5

ISP mail

MSR5

Users

MS R5

Specs

DS R5

Users

DS R5

Dbase2

DS R1

Logs

DS R5

Dbase1

3-6

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

Planning Applications, LUNs, and Storage Groups

This section helps you plan your shared storage use — the

applications to run, the LUNs that will hold them, and the Storage

Groups that will belong to each server. The worksheets to help you

do this include

•Application and LUN planning worksheet - lets you outline your

storage needs.

•LUN and Storage Group planning worksheet - lets you decide on

the disks to compose the LUNs and the LUNs to compose the

Storage Groups for each server.

•LUN details worksheet - lets you plan each LUN in detail.

Make as many copies of each blank worksheet as you need. You will

need this information later when you configure the shared storage

system.

Sample worksheets appear later in this chapter.

Application and LUN Planning

Use the following worksheet to list the applications you will run and

the RAID type and size of LUN to hold them. For each application

that will run in the SAN, write the application name, file system (if

any), RAID type, LUN ID (ascending integers, starting with 0), disk

space required, and finally the name of the servers and operating

systems that will use the LUN.

Planning Applications, LUNs, and Storage Groups

3-7

Planning File Systems and LUNs with Shared Switched Storage

Application and LUN Planning Worksheet

A sample worksheet begins as follows:

Completing the Application and LUN Planning Worksheet

Application. Enter the application name or type.

File system, partition, or drive. Write the drive letter (for Windows

only) and the partition, file system, logical volume, or drive letter

name, if any.

With a Windows operating system, the LUNs are identified by drive

letter only. The letter does not help you identify the disk

configuration (such as RAID 5). We suggest that later, when you use

the operating system to create a partition on a LUN, you use the disk

administrator software to assign a volume label that describes the

RAID configuration. For example, for drive T, assign the volume ID

RAID5_T. The volume label will then identify the drive letter.

Application

File system,

partition, or drive

RAID type of

LUN

ID (hex)

Disk space

required

(Gbytes)

Server name and

operating system

Application

File system,

partition, or drive

RAID type of

LUN

ID (hex)

Disk space

required

(Gbytes)

Server name and

operating system

il 1 R

ID 5 0

ver

1, NT

il 2 R

ID 5 1

ver

1, NT

Database index R

D 1 2

ver

2, NT

3-8

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

RAID type of LUN. This is the RAID Group type you want for this

partition, file system, or logical volume. The features of RAID types

are explained in Chapter 2. For a RAID 5, RAID 1, RAID 1/0, and

RAID 0 Group, you can create one or more LUNs on the RAID

Group. For other RAID types, you can create only one LUN per RAID

Group.

LUN ID. The LUN ID is a hexadecimal number assigned when you

bind the disks into a LUN. By default, the ID of the first LUN bound

is 0, the second 1, and so on. Each LUN ID must be unique within the

storage system, regardless of its Storage Group or RAID Group.

The maximum number of LUNs supported on one host-bus adapter

depends on the operating system.

Disk space required (Gbytes). Consider the largest amount of disk

space this application will need, then add a factor for growth.

Server hostname and operating system. Enter the server hostname

(or, if you don’t know the name, a short description that identifies the

server) and the operating system name, if you know it.

LUN and Storage Group Planning Worksheet

Use the following worksheet to select the disks that will make up the

LUNs and Storage Groups in the SAN. A shared storage system can

include up to 100 disks, numbered 0 through 99, left to right from the

bottom up.

Planning Applications, LUNs, and Storage Groups

3-9

Planning File Systems and LUNs with Shared Switched Storage

LUN and Storage Group Planning Worksheet

Storage Group ID or name:______ Server hostname:_____________________ Dedicated Shared

LUN ID or name_______RAID type ___ Cap. (Gb) _____ Disk IDs_________________________________________

0_0 0_1 0_2 0_3 0_4 0_5 0_6 0_7 0_8 0_9

1_0 1_1 1_2 1_3 1_4 1_5 1_6 1_7 1_8 1_9

2_0 2_1 2_2 2_3 2_4 2_5 2_6 2_7 2_8 2_9

3_0 3_1 3_2 3_3 3_4 3_5 3_6 3_7 3_8 3_9

4_0 4_1 4_2 4_3 4_4 4_5 4_6 4_7 4_8 4_9

5_0 5_1 5_2 5_3 5_4 5_5 5_6 5_7 5_8 5_9

6_0 6_1 6_2 6_3 6_4 6_5 6_6 6_7 6_8 6_9

7_0 7_1 7_2 7_3 7_4 7_5 7_6 7_7 7_8 7_9

8_0 8_1 8_2 8_3 8_4 8_5 8_6 8_7 8_8 9_9

9_0 9_1 9_2 9_3 9_4 9_5 9_6 9_7 9_8 9_9

10_0 10_1 10_210_3 10_4 10_5 10_610_7 10_8 10_9

11_0 11_1 11_211_3 11_4 11_511_6 11_7 11_811_9

Storage system number or name:_______________

Storage Group ID or name:______ Server hostname:_____________________ Dedicated Shared

LUN ID or name_______RAID type ___ Cap. (Gb) _____ Disk IDs_________________________________________

Storage Group ID or name:______ Server hostname:_____________________ Dedicated Shared

LUN ID or name_______RAID type ___ Cap. (Gb) _____ Disk IDs_________________________________________

3-10

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

Part of a sample LUN and Storage Group worksheet follows.

Completing the LUN and Storage Group Planning Worksheet

As shown, draw circles around the disks that will compose each

LUN, and within each circle specify the RAID type (for example,

RAID 5) and LUN ID. This is information you will use to bind the

disks into LUNs. For disk IDs, use the form shown. This form is

enclosure_diskID, where enclosure is the enclosure number (the bottom

one is 0, above it 1, and so on) and diskID is the disk position (left is 0,

next is 1, and so on).

None of the disks 0_0 through 0_8 may be used as a hot spare.

Next, complete as many of the Storage System sections as needed for

all the Storage Groups in the SAN. Copy the (blank) worksheet as

needed for all Storage Groups in each storage system.

A storage system is any group of enclosures connected to a DPE; it

can include up to 11 DAE enclosures for a total of 120 disks. If a

Storage Group ID or name:______ Server hostname:_____________________ Dedicated Shared

LUN ID or name_______RAID type ___ Cap. (Gb) _____ Disk IDs_____________________________

0_0 0_1 0_2 0_3 0_4 0_5 0_6 0_7 0_8 0_9

1_0 1_1 1_2 1_3 1_4 1_5 1_6 1_7 1_8 1_9

2_0 2_1 2_2 2_3 2_4 2_5 2_6 2_7 2_8 2_9

3_0 3_1 3_2 3_3 3_4 3_5 3_6 3_7 3_8 3_9

Storage system number or name:_______________

Storage Group ID or name:______ Server hostname:_____________________ Dedicated Shared

LUN ID or name_______RAID type ___ Cap. (Gb) _____ Disk IDs_____________________________

LUN 0

RAID 5

LUN 1

RAID 5

LUN 2

RAID 1

Server1

Server2

Mail 1

0_0, 0_1, 0_2, 0_3, 0_4

Index1

0_5, 0_6, 0_7, 0_8, 0_9

1_0, 1_1

SS1

Planning Applications, LUNs, and Storage Groups

3-11

Planning File Systems and LUNs with Shared Switched Storage

Storage Group will be dedicated (not accessible by another system in

a cluster), mark the Dedicated box at the end of its line; if the Storage

Group will be accessible to one or more other servers in a cluster,

write the hostnames of all servers and mark the Shared box.

LUN Details Worksheet

Use the following LUN details worksheet to plan the individual

LUNs. Complete as many of these as needed for all LUNs in your

SAN.

3-12

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

LUN Details Worksheet

Storage system (complete this section once for each storage system)

Storage-system number or name:______

Storage-system installation type

❏Unshared Direct ❏Shared-or-Clustered Direct ❏Shared Switched

SP FC-AL address ID (unshared only): SP A:_____SP B:_____

SP memory (Mbytes): SP A:___ SP B:____

❏Use for caching Read cache size:__ MB Write cache size: __ MB Cache page size:___KB

❏Use for RAID 3

LUN ID:_____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

LUN ID:____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

LUN ID:____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

Planning Applications, LUNs, and Storage Groups

3-13

Planning File Systems and LUNs with Shared Switched Storage

LUN Details Worksheet

Storage system (complete this section once for each storage system)

Storage-system number or name:__SS1____

Storage-system installation type

❏Unshared Direct ❏Shared-or-Clustered Direct ❏Shared Switched

SP FC-AL address ID (unshared only): SP A:_____SP B:_____

SP memory (Mbytes): SP A:_256__ SP B:_256__

❏Use for caching Read cache size:_80_ MB Write cache size: _160_ MB Cache page size:_2__KB

❏Use for RAID 3

LUN ID:__0___

RAID Group ID: 0Size,GB: 72 LUN size,GB: 72 Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: T

LUN ID:__1__

RAID Group ID: 1 Size,GB: 72 LUN size,GB: 72 Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: U

LUN ID:__2__

RAID Group ID: 2Size,GB: LUN size,GB: 18 Disk IDs: SP: ❏A❏B

RAID type: ❏RAID 5 ❏RAID 3 - Memory, MB:___ ❏RAID 1 mirrored pair ❏RAID 0

❏RAID 1/0 ❏Individual disk ❏Hot spare

Caching: ❏Read and write ❏Write ❏Read ❏None

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: V

0_0,0_1,0_2,0_3,0_4

1_0, 1_1

0_5, 0_6, 0_7, 0_8, 0_9

3-14

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

Completing the LUN Details Worksheet

Complete the header portion of the worksheet for each storage

system as described below. Copy the blank worksheet as needed.

Storage-system entries

Storage-system installation type, specify Shared Switched

storage.

SP FC-AL address ID. This does not apply to shared storage, in

which the switch determines the address of each device.

Use memory for caching. You can use SP memory for read/write

caching or RAID 3. (Using both caching and RAID 3 in the same

storage system is not recommended.) You can use different cache

settings for different times of day (for example, for user I/O

during the day, use more write cache; for sequential batch jobs at

night, use more read cache. You enable caching for specific LUNs

— allowing you to tailor your cache resources according to

priority. If you choose caching, check the box and continue to the

next step; for RAID 3, skip to the RAID Group ID entry.

Read cache size. If you want a read cache, it should generally be

about one third of the total available cache memory.

Write cache size. The write cache should be two thirds of the total

available. Some memory is required for system overhead, so you

cannot determine a precise figure at this time. For example, for

256 Mbytes of total memory, you might have 240 Mbytes

available, and you would specify 80 Mbytes for the read cache

and 160 Mbytes for the write cache.

Cache page size. This applies to both read and write caches. It can

be 2, 4, 8, or 16 Kbytes. As a general guideline, we suggest

•For a general-purpose file server — 8 Kbytes

•For a database application — 2 or 4 Kbytes

The ideal cache page size depends on the operating system and

application.

Use memory for RAID 3. If you want to use the SP memory for

RAID 3, check the box.

RAID Group/LUN Entries

Complete a RAID Group/LUN entry for each LUN and hot spare.

Planning Applications, LUNs, and Storage Groups

3-15

Planning File Systems and LUNs with Shared Switched Storage

LUN ID. The LUN ID is a hexadecimal number assigned when

you bind the disks into a LUN. By default, the ID of the first LUN

bound is 0, the second 1, and so on. Each LUN ID must be unique

within the storage system, regardless of its Storage Group or

RAID Group.

The maximum number of LUNs supported on one host-bus

adapter depends on the operating system.

RAID Group ID. This ID is a hexadecimal number assigned

when you create the RAID Group. By default, the number of the

first RAID Group in a storage system is 0, the second 1, and so on,

up to the maximum of 1F (31).

Size (RAID Group size). Enter the user-available capacity in

gigabytes (Gbytes) of the whole RAID Group. You can determine

the capacity as follows:

For example,

•A five-disk RAID 5 or RAID 3 Group of 36-Gbyte disks holds

144 Gbytes;

•An eight-disk RAID 1/0 Group of 36-Gbyte disks also holds

144 Gbytes;

•A RAID 1 mirrored pair of 36-Gbyte disks holds 36 Gbytes;

and

•An individual disk of an 36-Gbyte disk also holds 36 Gbytes.

Each disk in the RAID Group must have the same capacity;

otherwise, you will waste disk storage space.

LUN size. Enter the user-available capacity in gigabytes (Gbytes)

of the LUN. You can make this the same size as the RAID Group,

above. Or, for a RAID 5, RAID 1, RAID 1/0, or RAID 0 Group,

you can make the LUN smaller than the RAID Group. You might

do this if you wanted a RAID 5 Group with a large capacity and

wanted to place many smaller capacity LUNs on it; for example,

to specify a LUN for each user. However, having multiple LUNs

RAID5 or RAID-3 Group: disk-size * (number-of-disks - 1)

RAID 1/0 or RAID-1 Group: (disk-size * number-of-disks) / 2

RAID 0 Group: disk-size * number-of-disks

Individual unit: disk-size

3-16

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

per RAID Group may adversely impact performance. If you want

multiple LUNs per RAID Group, then use a RAID Group/LUN

series of entries for each LUN.

Disk IDs. Enter the ID(s) of all disks that will make up the LUN

or hot spare. These are the same disk IDs you specified on the

previous worksheet. For example, for a RAID 5 Group in the DPE

(enclosure 0, disks 2 through 6), enter 0_2, 0_3, 0_4, 0_5, and 0_6.

SP. Specify the SP that will own the LUN: SP A or SP B. You can

let the management program automatically select the SP to

balance the workload between SPs; to do so, leave this entry

blank.

RAID type. Copy the RAID type from the previous worksheet.

For example, RAID 5 or hot spare. For a hot spare (not strictly

speaking a LUN at all), skip the rest of this LUN entry and

continue to the next LUN entry (if any).

If this is a RAID 3 Group, specify the amount of SP memory for

that group. To work efficiently, each RAID 3 Group needs at least

6 Mbytes of memory.

Caching. If you want to use caching (entry on page 3-14), you can

specify whether you want caching — read and write, read, or

write for this LUN. Generally, write caching improves

performance far more than read caching. The ability to specify

caching on a LUN basis provides additional flexibility, since you

can use caching for only the units that will benefit from it. Read

and write caching recommendations follow.

Table 3-1 Cache Recommendations for Different RAID Types

Servers that can access this LUN. Enter the name of each server

(copied from the LUN and Storage Group worksheet).

Operating system information: Device name. Enter the

operating system device name, if this is important and if you

know it. Depending on your operating system, you may not be

able to complete this field now.

RAID 5 RAID 3 RAID 1 RAID 1/0 RAID 0 Individual Unit

Highly Recommended Not allowed Recommended Recommended Recommended Recommended

Planning Applications, LUNs, and Storage Groups

3-17

Planning File Systems and LUNs with Shared Switched Storage

File system, partition, or drive. Write the name of the file system,

partition, or drive letter you will create on this LUN. This is the

same name you wrote on the application worksheet.

On the following line, write any pertinent notes; for example, the

file system mount- or graft-point directory pathname (from the

root directory). If this storage system’s chassis will be shared with

another server, and the other server is the primary owner of this

disk, write secondary. (As mentioned earlier, if the storage system

will be used by two servers, we suggest you complete one of

these worksheets for each server.)

What Next? This chapter outlined the planning tasks for shared storage systems.

If you have completed the worksheets to your satisfaction, you are

ready to learn about the hardware needed for these systems as

explained in Chapter 5.

3-18

EMC Fibre Channel Storage-System Configuration Planning

Planning File Systems and LUNs with Shared Switched Storage

Planning LUNs and File Systems with Unshared Direct Storage

4-1

Invisible Body Tag

This chapter shows sample RAID and LUN configurations with

direct storage installations and then provides worksheets for

planning your own storage installation. Topics are

•Dual SPs and Paths to LUNs............................................................4-2

•Unshared Direct and Shared-or-Clustered Direct Storage...........4-2

•Planning Applications and LUNs ...................................................4-4

Planning LUNs and File

Systems with Unshared

Direct Storage

4-2

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

Dual SPs and Paths to LUNs

If a storage system has two SPs, there are two routes to its LUNs. If

the server has two adapters and the storage system has two SPs,

Application Transparent Failover (ATF). ATF can automatically

switch to the other path, without disrupting applications, if a device

(such as a host-bus adapter, cable, or SP) fails.

Unshared Direct and Shared-or-Clustered Direct Storage

This section explains the direct (unswitched) options available for

connecting storage systems to servers. As needs change, you may

want to change a configuration. You can do so without changing your

LUN configuration or losing user data.

There are two types of installation:

•Unshared direct with one server is the simplest and least costly;

•Shared-or-clustered direct lets two clustered servers share

storage resources with high availability.

Sample Unshared Direct Installation

Figure 4-1 Unshared Direct Installation

EMC1825

Disk IDs

100-109

010-019

Database

RAID 5 Users

RAID 5

Sys

RAID 1

Clients, mail

RAID 5

SP A SP B

Adapter

Server

Path 1

Path 2

Unshared Direct and Shared-or-Clustered Direct Storage

4-3

Planning LUNs and File Systems with Unshared Direct Storage

The storage system disk IDs and LUNs are as follows. The LUN

capacities shown assume 36-Gbyte disks.

Sample Shared-or-Clustered Direct Installation

Figure 4-2 Sample Clustered Installation

If each disk holds 36 Gbytes, then the storage-system chassis provides

Server 1 with 256 Gbytes of disk storage, 220 Gbytes highly available;

it provides Server 2 with 216 Gbytes of storage, all highly available.

Each server has its own SP, which controls that server’s LUNs; those

LUNs remain primary to that server. The LUNs are as follows.

LUNs - SP A and SP B, 422 Gbytes

Disk IDs RAID type, storage type, capacity

0_0, 0_1 RAID 1, System disk, 36 Gbytes

0_2-0_9 RAID 5 (8 disks), Clients and Mail, 216 Gbytes

1_0-1_4 RAID 5, Database, 144 Gbytes

1_5 Disk, Temporary storage, 36 Gbytes

Path 2

Path 1

Server 2 (S2)

Server 1 (S1)

Storage

system

S1Mail

RAID1

S2 Customers

RAID 5

S1Dbase

RAID 5

Unused

Spare

S2 Usri

RAID1

SP A SP B

Adapter

Server1 LUNs (S1) - SP A, 256 Gbytes Server2 LUNs (S2) - SP B, 216 Gbytes

Disk IDs RAID type, storage type, capacity

0_0, 0_1 RAID 1, System disk, 36 Gbytes

0_2 Disk, Temporary storage, 36 Gbytes

0_3-0_7 RAID 5, Database, 144 Gbytes

0_8-0_ 9 RAID 1, Users, 36 Gbytes

Disk IDs RAID type, storage type, capacity

1_0-1_7 RAID 5 (8 disks), Cust Accounts, 216

Gbytes

4-4

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

Planning Applications and LUNs

This section helps you plan your unshared (direct) storage use —

applications you want to run and the LUNs that will hold them. The

worksheets to help you do this include

•Application and file system planning worksheet - lets you outline

your storage needs.

•LUN planning worksheet - lets you decide on the disks that will

compose the LUNs.

•LUN details worksheet - lets you plan each LUN in detail.

Make as many copies of each blank worksheet as you need. You will

need this information later when you configure the shared storage

system.

Sample file system, Storage Group, and LUN worksheets appear later

in this chapter.

Application and LUN Planning

Use the following worksheet to plan your file systems and RAID

types. For each application, write the application name, file system (if

any), RAID type, LUN ID (ascending integers, starting with 0), disk

space required, and finally the name of the servers and operating

systems that will use the LUN.

Planning Applications and LUNs

4-5

Planning LUNs and File Systems with Unshared Direct Storage

Application and LUN Planning Worksheet

A sample worksheet begins as follows:

Completing the Application and LUN Planning Worksheet

Application. Enter the application name or type.

File system, partition, or drive. Write the drive letter (for Windows

only) and the partition, file system, logical volume, or drive letter

(Windows only) name.

With a system such as Windows NT, the LUNs are identified by drive

letter only. The letter does not help you identify the disk

configuration (such as RAID 5). We suggest that later, when you use

the operating system to create a partition on the unit, you use the disk

administrator software to assign a volume label that describes the

Application File system (if any)

RAID type of

LUN

ID (hex)

Disk space

required

(Gbytes)

Server name and

operating system

Application File system (if any)

RAID type of

LUN

ID (hex)

Disk space

required

(Gbytes)

Server name and

operating system

il 1 R

I D 5 0

ver

1, NT

il 2 R

I D 5 1

ver

1, NT

Database index R

D 1 2

ver

2, NT

4-6

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

RAID configuration. For example, for drive T, assign the volume ID

RAID5_T. The volume label will then identify the drive letter.

RAID type of LUN is the RAID Group type you want for this

partition, file system, or logical volume. The features of RAID types

are explained in Chapter 2. For a RAID 5, RAID 1, RAID 1/0, and

RAID 0 Group, you can create one or more LUNs on the RAID

Group. For other RAID types, you can create only one LUN per RAID

Group.

LUN ID is a hexadecimal number assigned when you bind the disks

into a LUN. By default, the ID of the first LUN bound is 0, the second

1, and so on. Each LUN ID must be unique within the storage system,

regardless of its Storage Group or RAID Group.

The maximum number of LUNs supported on one host-bus adapter

depends on the operating system. Some systems allow only eight

LUNs (numbers 0 through 7). For an operating system with this

restriction, if you want a hot spare, assign the hot spare an ID above

7; for example, 8 or 9. The operating system never accesses a hot

spare, so the ID is irrelevant to it.

Disk space required (Gbytes), Consider the largest amount of disk

space this application will need, then add a factor for growth.

Server hostname and operating system Enter the server hostname

(or, if you don’t know the name, a short description that identifies the

server) and the operating system name, if you know it.

If this storage system will be used by two servers, provide a copy of

this worksheet to the other server. This is particularly important

where one server may take over the other’s LUNs. If a LUN will be

shared, on the Notes section of the LUN details worksheet, write

Primary to server-name or Secondary to server-name.

LUN Planning Worksheet

Use one of the following worksheets (Rackmount or Deskside) to

select the disks that will make up the LUNs. Depending on model, a

full-fibre rackmount storage system can include up to 100 disks,

numbered 0 through 99, left to right from the bottom up.

Again depending on model, a deskside storage system can hold ten,

20, or 30 disks.

Planning Applications and LUNs

4-7

Planning LUNs and File Systems with Unshared Direct Storage

LUN Planning Worksheet - Rackmount

Full-fibre storage system

0_0 0_1 0_2 0_3 0_4 0_5 0_6 0_7 0_8 0_9

1_0 1_1 1_2 1_3 1_4 1_5 1_6 1_7 1_8 1_9

2_0 2_1 2_2 2_3 2_4 2_5 2_6 2_7 2_8 2_9

3_0 3_1 3_2 3_3 3_4 3_5 3_6 3_7 3_8 3_9

4_0 4_1 4_2 4_3 4_4 4_5 4_6 4_7 4_8 4_9

5_0 5_1 5_2 5_3 5_4 5_5 5_6 5_7 5_8 5_9

6_0 6_1 6_2 6_3 6_4 6_5 6_6 6_7 6_8 6_9

7_0 7_1 7_2 7_3 7_4 7_5 7_6 7_7 7_8 7_9

8_0 8_1 8_2 8_3 8_4 8_5 8_6 8_7 8_8 8_9

9_0 9_1 9_2 9_3 9_4 9_5 9_6 9_7 9_8 9_9

10_0 10_1 10_2 10_3 10_4 10_5 10_6 10_7 10_8 10_9

11_0 11_1 11_2 11_3 11_4 11_5 11_6 11_7 11_8 11_9

LUN number_______RAID type ___ Cap. (Gb) _____ Disk IDs_________________________________________

4-8

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

LUN Planning Worksheet - Deskside

1_4

1_2

1_1

1_3

1_5

1_9

1_8

1_7

1_6

Full-fibre storage system

2_4

2_2

2_1

2_3

2_5

2_9

2_8

2_7

2_6

0_0

0_1

0_2

0_3

0_4

0_5

0_6

0_7

0_8

0_9

1_0 2_0

LUN number_______RAID type ___ Cap. (Gb) _____ Disk IDs_______________________________________

Storage system number_____

Planning Applications and LUNs

4-9

Planning LUNs and File Systems with Unshared Direct Storage

A sample LUN worksheet follows.

Completing the LUN Planning Worksheet

As shown, draw circles around the disks that will compose each

LUN, and within each circle specify the RAID type (for example,

RAID 5) and LUN ID. This is information you will use to bind the

disks into LUNs. For disk IDs, use the form shown. This form is

enclosure_diskID, where enclosure is the enclosure number (the bottom

one is 0, above it 1, and so on) and diskID is the disk position (left is 0,

next is 1, and so on).

None of the disks 0_0 through 0_8 may be used as a hot spare.

Next, complete as many of the LUN sections as needed for each

storage system.Copy the (blank) worksheet as needed for all LUNs in

each storage system. A storage system is any group of enclosures

connected to a DPE; a full-fibre system can include up to nine DAE

enclosures for a total of 100 disks.

LUN Details Worksheet Use the following LUN details worksheet to plan the individual

LUNs. Complete as many of these as needed for all LUNs.

0_0 0_1 0_2 0_3 0_4 0_5 0_6 0_7 0_8 0_9

1_0 1_1 1_2 1_3 1_4 1_5 1_6 1_7 1_8 1_9

2_0 2_1 2_2 2_3 2_4 2_5 2_6 2_7 2_8 2_9

LUN number_______RAID type ___ Cap. (Gb) _____ Disk IDs_________________________________________

LUN 0

RAID 5

LUN 1

RAID 5

LUN 2

RAID 1

0_0, 0_1, 0_2, 0_3, 0_4

144 0_5, 0_6, 0_7, 0_8, 0_9

144

21_0, 1_1

4-10

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

LUN Details Worksheet

Storage system (complete this section once for each storage system)

Storage-system number or name:______

Storage-system installation type

❏Unshared Direct ❏Shared-or-Clustered Direct ❏Shared Switched

SP FC-AL address ID (unshared only): SP A:_____SP B:_____

SP memory (Mbytes): SP A:______ SP B:______

VUse for caching Read cache size:___ MB Write cache size: ___ MB Cache page size:___KB

VUse for RAID 3

LUN ID:_____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

LUN ID:_____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

LUN ID:_____

RAID Group ID: Size,GB: LUN size,GB: Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN:

Operating system information: Device name: File system, partition, or drive:

Planning Applications and LUNs

4-11

Planning LUNs and File Systems with Unshared Direct Storage

LUN Details Worksheet

Storage system (complete this section once for each storage system)

Storage-system number or name:__1____

Storage-system installation type

❏Unshared Direct ❏Shared-or-Clustered Direct ❏Shared Switched

SP FC-AL address ID (unshared only): SP A:_____SP B:_____

SP memory (Mbytes): SP A:_128__ SP B:_128__

VUse for caching Read cache size:_40_ MBWrite cache size: _80_ MBCache page size:_2__KB

VUse for RAID 3

LUN ID:__0___

RAID Group ID: 0Size,GB: 144 LUN size,GB: 144 Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: T

LUN ID:__1__

RAID Group ID: 1 Size,GB: 144 LUN size,GB: 144 Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: U

LUN ID:__2__

RAID Group ID: 2Size,GB: LUN size,GB: 36 Disk IDs: SP: VAVB

RAID type: VRAID 5 VRAID 3 - Memory, MB:___ VRAID 1 mirrored pair VRAID 0

VRAID 1/0 VIndividual disk VHot spare

Caching: VRead and write VWrite VRead VNone

Servers that can access this LUN: Server1

Operating system information: Device name: File system, partition, or drive: V

0_0, 0_1, 0_2, 0_3, 0_4

0_5, 0_6, 0_7, 0_8, 0_9

1_0, 1_1

4-12

EMC Fibre Channel Storage Systems Configuration Planning Guide

Planning LUNs and File Systems with Unshared Direct Storage

Completing the LUN Details Worksheet

Complete the header portion of the worksheet for each storage

system as described below. Copy the blank worksheet as needed.

Sample completed LUN worksheets appear later.

Storage-System Entries

Storage-system configuration. Specify Unshared Direct (one server)

or Shared-or-Clustered Direct (two servers).

For any multiple-server configuration, each server will need cluster

software.

SP FC-AL address ID. For unshared storage, which uses FC-AL

addressing, each SP (and each other node) on a Fibre Channel loop

must have a unique FC-AL address ID. You set the SP FC-AL address

ID using switches on the back panel of the SP. The valid FC-AL

address ID range is a number 0 through 125 decimal, which is 0

through 7D hexadecimal. For any number above 9, we suggest

hexadecimal, since the switches are marked in hexadecimal.

If you have two FC-AL loops, we suggest a unique FC-AL address ID

for each SP on both loops.

SP memory. Enter the amount of memory each SP has. If a storage

system has two SPs, they will generally have the same amount of

memory. You can allocate this memory to storage-system caching or

RAID 3 use.

Use memory for caching. You can use SP memory for read/write

caching or RAID 3. (Using both caching and RAID 3 in the same

storage system not recommended.) You can use different cache

settings for different times of day (for example, for user I/O during

the day, use more write cache; for sequential batch jobs at night, use

more read cache. You enable caching for specific LUNs — allowing

you to tailor your cache resources according to priority. If you choose

caching, check the box and continue to the next step; for RAID 3, skip

to the RAID Group ID entry.

Read cache size. If you want a read cache, it should generally be

about one third of the total available cache memory.

Write cache size. The write cache should be two thirds of the total

available. Some memory is required for system overhead, so you

cannot determine a precise figure at this time. For example, for 256

Mbytes of total memory, you might have 240 Mbytes available, and

Planning Applications and LUNs

4-13

Planning LUNs and File Systems with Unshared Direct Storage

you would specify 80 Mbytes for the read cache and 160 Mbytes for

the write cache.

Cache page size. This applies to both read and write caches. It can be

2, 4, 8, or 16 Kbytes. As a general guideline, we suggest

For a general-purpose file server — 8 Kbytes

For a database application — 2 or 4 Kbytes