Temperature only matters at the INLET…

DC Temperature

Data Center temperature is a 'hot' topic today!

I have sat in on several customer discussions this past year where data center operations and facilities managers are looking for ways to save energy and align their efforts towards more cost-effective operations. Undoubtably, the data center temperature becomes one of the biggest topics at hand. What I find interesting is that a fairly significant mental disconnect exists between room temperature and inlet temperature for the IT gear. Everyone wants to talk about room temperature or fairly large zones. Very macro. These zones typically map to where CRAC units are deployed.

A few times I toss out the idea that as a general rule, the temperature of the actual ROOM  does NOT matter. I explain that within OSHA limits, the room itself could be 40-degrees F or a 140-degrees F. It just doesn’t matter AS LONG AS the INLET temperature of the active devices are within the Data Center IT Goldilocks zone (I am using NASA’s Goldilocks term to refer to ASHRAE’s TC9.9 Data Center A1 spec of 64-degrees to 80-degrees. This is where we want our IT gear to ‘live’.)

Common sense makes everyone smile and in a few cases, the direction of discussion changes a bit towards data center monitoring possibilities at a more granular level. The idea being that the closer to each inlet you can monitor, the more likely you will know how to adjust cooling systems to set these micro-zones to the Goldilocks values. In the past granular monitoring was difficult and expensive. Not today! Wired and wireless systems sensor can be easily deployed that allow half a dozen sense points to be measured per RACK, which almost assures that the INLET temperature will be known.  (Many server, switch and storage vendors can also now report their INLET temperature with increasing accuracy). Once the INLET micro-zones are understood, attention can be turned to the cooling strategy to determine if these small zones can be cooled appropriately. (In many cases for older data centers, they can NOT be controlled very efficiency since the number of CRAC units installed within the room is too small. A small number of CRAC units lessens the ability to cool smaller zones).

It all starts with better monitoring, and a desire to do thing differently…

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Mark Harris Fremont, CA
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