Fluke 975 Application Note

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Application Note

Monitoring temperature,

humidity, and airflow

in data centers

A market in need of measurement

From the Fluke Digital Library @ www.fluke.com/library

Using a Fluke Ti20 Thermal Imager and a

Fluke 975V AirMeter™ test tool, customers

protect their servers by monitoring envi-

ronments in rented data centers.

The international law firm

depicted in this story owns no

data centers, despite the large

amount of data it stores and

retrieves. Like many other high-

tech companies, it rents space for

its servers in data centers owned

by others. “The sites we use are

just hosts,” says the law firm’s

data center support analyst. “The

racks we have there are ours, but

we rent the environment, power

and the bandwidth.”

Each of the firm’s offices has

one or two racks of servers in a

local data center to service that

site’s needs. In addition, the

company has a centralized U.S.

server location, a secondary cen-

ter for backup and redundancy,

and plans for new locations

overseas.

Fluke instruments used

At present, the analyst uses two

Fluke instruments to monitor the

firm’s data centers and the status

of its servers in those centers:

The Fluke 975 AirMeter can

record ten fundamental param-

eters associated with indoor air

quality. Of special importance to

data centers are air temperature,

relative humidity, and airflow (air

velocity). Since servers generate

considerable heat, they must be

cooled to manufacturer-specified

temperatures and subjected to no

more than 45 to 50 percent rela-

tive humidity.

2 Fluke Corporation Monitoring temperature, humidity, and airflow in datacenters

The Fluke Ti20 Thermal

Imager makes two-dimensional

representations of the surface

temperatures of objects in an

infrared image. The support

analyst uses the Ti20 to monitor

data centers for general cool-

ing efficiency and to inspect law

firm’s servers in those centers.

Software that comes with the

imager allows him to change key

parameters, optimize images, and

extract maximum details from

collected data.

Problems and solutions

As the law firm seeks to expand

its data handling capabilities,

the biggest problem the support

analyst faces is that data centers

lack the required power and

cooling capabilities to support

new technologies.

“We want to take advantage

of the latest blade servers, but

it’s difficult to find data centers

that can support them,” he says.

“Blade servers are much more

efficient [than traditional serv-

ers]. We can pack six or seven

virtual servers onto a single

blade. An enclosure or rack

holds eight blades, but each full

enclosure requires a lot of power.

Many data centers simply can’t

supply that power. They want

us to use an older technology so

they can support our needs.”

Blade servers also produce

considerable heat and require

more cooling than many cen-

ters can supply. In such cases,

the analyst uses the Fluke Ti20

and Fluke 975 to 1) map cool-

ing patterns in data centers, 2)

find faulty cooling arrangements

and 3) determine when cooling,

air flow and air temperatures

are inadequate to guard against

breaches of server warranties.

Mapping cooling patterns

allows company personnel to

see the overall effects of cooling

within a data center. This may

seem like a duplication of effort,

since data centers themselves

monitor the environmentals—

power, air, humidity, cooling, etc.

However, “our primary use for

these tools is to check what we

are told by the data centers,” the

analyst says. “Then, if necessary,

we can suggest corrective mea-

sures to keep our servers func-

tioning efficiently.”

The support analyst cites the

local data center as an example:

“The way the room is set up

right now greatly restricts the air

flow going to some of the devices

positioned across the room from

the air-conditioning unit. Using

the Ti20, we were able to take

temperature readings of surfaces

in each area of the room. Then,

using those readings, we were

able to plot out where the cool

air travels. We found that while

one area of the room is cold,

as we worked our way around

the room, areas were gradually

warmer and warmer.”

He says that the Fluke 975

AirMeter used in conjunction

with the Ti20 allowed for a

more in-depth analysis of the

local data center: “Temperature

and humidity readings indicated

that the hot air that should be

exhausted from the room is actu-

ally being dumped back into the

room in an endless cycle. The

air-conditioner cools itself down

and shuts off. But the circulation

fans keep working. They actu-

ally kick the hot air back into the

room. Overall, it’s a very poorly

designed room. We’re looking to

the data center to restructure the

cooling system.”

Finding faulty cooling

arrangements for the law firm’s

servers is another of the analyst’s

uses for the Ti20. “Because of the

cooling requirements for blade

servers, we have been using the

Ti20 to monitor the temperatures

of the air flowing into the fronts

and out the backs of our blade

racks,” he says.

A common problem experi-

enced by their blade servers is

hot air entering the front of the

blades. Only cooling air should

be entering the rack fronts.

Two situations that lead to this

problem are 1) missing blanks

on empty rack slots and 2)

server aisles set up with servers

arranged front to back.

Using the Ti20 to scan

heat output from the

backside of blade servers.

3 Fluke Corporation Monitoring temperature, humidity, and airflow in datacenters

The first situation usually

occurs because a user of the data

center does not need all eight

slots in a rack or because the

data center lacks the capability

to provide power to a full rack.

In either case, there are empty

slots. Blanking panels should

cover those unused slots so that

they are not open to the environ-

ment.

The analyst says that he has

documented instances of miss-

ing blanking panels at the firm’s

secondary center. “There were

empty spaces on the top four

slots,” he says. “Nobody could

believe it, but hot air from the

backs of the servers was circu-

lating over the tops of the racks

and coming right back in the

front. That greatly increased the

temperature of the blades and

decreased their efficiency. We

needed to fill the tops of those

racks with blanking plates.”

The best strategy for a data

center—especially a data center

with blade servers—is to install

servers back-to-back in rows

facing the fronts of servers in

adjacent rows. This creates alter-

nating cold aisles and hot aisles.

“A lot of data centers are set

up with one row of servers after

another—back to front, back to

front, back to front,” he says dis-

approvingly. “The hot air from

one row of servers blows onto

the fronts of the next row, and

that’s continued throughout the

center. In Europe, we are looking

for a center with alternating hot

and cold aisles.”

Safeguarding server war-

ranties is the analyst’s principal

impetus for monitoring the law

firm’s servers. “Our blade manu-

facturer has a recommended

maximum temperature that serv-

ers can reach. If a server gets

above that threshold, it is no lon-

ger covered under our warranties

and contracts. That would be a

huge problem for us.”

Because of these warranty

considerations, company per-

sonnel need to verify what data

center owners tell them about

the cooling in their facilities. And

while the blades themselves

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have internal monitors that track

their temperatures, the analyst

needs know how effectively the

cooling supplied by the data cen-

ter is doing the job.

He uses the Ti20 to collect

thermal images of the fronts

of the blades to determine the

temperature of the air flowing

in. Then, he compares this tem-

perature to the temperature of

the air coming out the back of

the rack. Finally, he compares

these temperatures to the blade

manufacturer’s recommended

temperature threshold for the

servers.

“If necessary,” he says, “we

can go back to a data center’s

owners and say, ‘This is the air-

flow that you are telling us we’re

getting, and this is what we see.

You’re not meeting our require-

ments. We need you to upgrade

your systems to make sure you

meet our specifications.’”

Additional capabilities

with the Fluke 975

The Fluke 975 AirMeter allows

the analyst to precisely measure

air temperatures and convert the

air-meter data into reports for

superiors or data center opera-

tors. Using the Ti20 Thermal

Imager and the 975 AirMeter

together “provides results from

different angles,” he says. “If we

use the imager to reveal the sur-

face temperatures, then we can

use the airflow meter to register

the actual temperature of the air

going into racks.”

The 975 AirMeter also mea-

sures relative humidity (RH)

and airflow. Excessive humid-

ity in a data center can lead

to condensation on equipment

and places an undue load on

the air-conditioning system. RH

readings played a significant

role in uncovering difficulties at

the local data center. Regard-

ing airflow, “In our primary and

secondary data centers, the air

comes in through the floors,”

he says. “We can use the air-

flow sensor on the 975 to make

sure that airflow is at the rate

required by our servers.”

Creating tracking

databases

The analyst’s job includes creat-

ing and maintaining tracking

databases. To do this, he peri-

odically uses the Ti20 to make

images at specific points in the

primary and secondary data cen-

ters. He then logs the data into

the database for review as nec-

essary. “We can graph the data

for each location and see if the

temperature is rising, falling or

staying the same over time,” he

explains.

Equipment frequently moves

within data centers, as clients

expand their server capacity or

stop using the center altogether.

If the law firm brings a new

piece of equipment into a data

center or reacts to a temperature

problem by moving an existing

server, the tracking database

allows them to assess how the

change affected ambient tem-

peratures.

From such findings, the sup-

port analyst, in cooperation with

data center personnel, can deter-

mine when the center needs

more cooling or when equip-

ment is packed in too densely.

In general, the database lets the

law firm and data center person-

nel pinpoint areas where the

air is more or less cool or where

there is more or less airflow. The

analyst speculates that as he

becomes more familiar with the

975 AirMeter and its data logging

capabilities, it will play a greater

role in his tracking databases.