Fluke 975 Application Note
2015-09-09
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Monitoring temperature, humidity, and airflow in data centers A market in need of measurement Application Note Using a Fluke Ti20 Thermal Imager and a Fluke 975V AirMeter ™ test tool, customers protect their servers by monitoring environments 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 hightech 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 center 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 parameters 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 relative humidity. From the Fluke Digital Library @ www.fluke.com/library are told by the data centers,” the analyst says. “Then, if necessary, we can suggest corrective measures to keep our servers functioning 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 Using the Ti20 to scan more in-depth analysis of the heat output from the local data center: “Temperature backside of blade servers. and humidity readings indicated that the hot air that should be exhausted from the room is actually being dumped back into the virtual servers onto a single The Fluke Ti20 Thermal room in an endless cycle. The blade. An enclosure or rack Imager makes two-dimensional air-conditioner cools itself down holds eight blades, but each full representations of the surface and shuts off. But the circulation enclosure requires a lot of power. fans keep working. They actutemperatures of objects in an Many data centers simply can’t infrared image. The support ally kick the hot air back into the analyst uses the Ti20 to monitor supply that power. They want room. Overall, it’s a very poorly us to use an older technology so designed room. We’re looking to data centers for general cooling efficiency and to inspect law they can support our needs.” the data center to restructure the Blade servers also produce firm’s servers in those centers. cooling system.” considerable heat and require Software that comes with the Finding faulty cooling imager allows him to change key more cooling than many cenarrangements for the law firm’s parameters, optimize images, and ters can supply. In such cases, servers is another of the analyst’s the analyst uses the Fluke Ti20 extract maximum details from uses for the Ti20. “Because of the and Fluke 975 to 1) map coolcollected data. cooling requirements for blade ing patterns in data centers, 2) servers, we have been using the Problems and solutions find faulty cooling arrangements Ti20 to monitor the temperatures and 3) determine when cooling, of the air flowing into the fronts As the law firm seeks to expand air flow and air temperatures and out the backs of our blade its data handling capabilities, are inadequate to guard against racks,” he says. the biggest problem the support breaches of server warranties. A common problem experianalyst faces is that data centers Mapping cooling patterns enced by their blade servers is lack the required power and allows company personnel to hot air entering the front of the cooling capabilities to support see the overall effects of cooling blades. Only cooling air should new technologies. within a data center. This may be entering the rack fronts. “We want to take advantage seem like a duplication of effort, Two situations that lead to this of the latest blade servers, but since data centers themselves problem are 1) missing blanks it’s difficult to find data centers monitor the environmentals— on empty rack slots and 2) that can support them,” he says. power, air, humidity, cooling, etc. server aisles set up with servers “Blade servers are much more However, “our primary use for arranged front to back. efficient [than traditional servthese tools is to check what we ers]. We can pack six or seven 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 environment. The analyst says that he has documented instances of missing 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 circulating 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 alternating 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 disapprovingly. “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 warranties is the analyst’s principal impetus for monitoring the law firm’s servers. “Our blade manufacturer has a recommended maximum temperature that servers can reach. If a server gets above that threshold, it is no longer covered under our warranties and contracts. That would be a huge problem for us.” Because of these warranty considerations, company personnel need to verify what data center owners tell them about the cooling in their facilities. And while the blades themselves have internal monitors that track their temperatures, the analyst needs know how effectively the cooling supplied by the data center 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 temperature 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 airflow that you are telling us we’re getting, and this is what we see. You’re not meeting our requirements. 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 operators. 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 surface temperatures, then we can use the airflow meter to register the actual temperature of the air going into racks.” The 975 AirMeter also measures relative humidity (RH) and airflow. Excessive humidity 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. Regarding airflow, “In our primary and secondary data centers, the air comes in through the floors,” he says. “We can use the airflow sensor on the 975 to make sure that airflow is at the rate required by our servers.” Fluke Corporation Monitoring temperature, humidity, and airflow in datacenters Creating tracking databases The analyst’s job includes creating and maintaining tracking databases. To do this, he periodically uses the Ti20 to make images at specific points in the primary and secondary data centers. He then logs the data into the database for review as necessary. “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 temperatures. From such findings, the support analyst, in cooperation with data center personnel, can determine when the center needs more cooling or when equipment is packed in too densely. In general, the database lets the law firm and data center personnel 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. Fluke. Keeping your world up and running.® Fluke Corporation PO Box 9090, Everett, WA USA 98206 Fluke Europe B.V. PO Box 1186, 5602 BD Eindhoven, The Netherlands For more information call: In the U.S.A. (800) 443-5853 or Fax (425) 446-5116 In Europe/M-East/Africa +31 (0) 40 2675 200 or Fax +31 (0) 40 2675 222 In Canada (800)-36-FLUKE or Fax (905) 890-6866 From other countries +1 (425) 446-5500 or Fax +1 (425) 446-5116 Web access: http://www.fluke.com ©2007 Fluke Corporation. All rights reserved. Specifications subject to change without notice. Printed in U.S.A. 5/2007 3034678 A-EN-N Rev A
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