Q&A: The man who helped raise server operating temperatures

Next month is the one year anniversary of a guideline by the American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE) that recommend increasing (PDF document) the temperature of air entering servers and other data center equipment. This increase of 77 degrees Fahrenheit to 80.6 degrees may not seem like a big deal, but it took a year-and-half of work to arrive at this recommendation and agreement by most of the major equipment vendors. The person who led the society's IT team on Technical Committee 9.9 was Roger Schmidt, an IBM fellow and its chief engineer for data center energy efficiency.

It's unknown how many data centers have adopted the recommendation, or even have enough control over their environments to safely regulate air flows. Ken Brill, executive director of the Uptime Institute in Santa Fe, New Mexico, said he sees more understanding that the data center temperatures can go up and says there has been a "very significant attitudinal change in a year," he said, but adds, that "many still don't know."

In an interview, Schmidt looked at the new temperature parameters, as well as some other issues involved in cooling data centers and reducing power usage.

How much heat can servers handle before they run into trouble? 

The previous guidelines for inlet conditions into server and storage racks was recommended at 68 degrees Fahrenheit to 77 Fahrenheit. This is where the IT industry feels that if you run at those conditions you will have reliable equipment for long periods of time. There is an allowable limit that is much bigger, from 59 degrees Fahrenheit to 89 degrees. That means that IT equipment will operate in that range, but if you run at the extremes of that range for long periods of time you may have some fails. We changed the recommended level -- the allowable levels remained the same -- to 64F to 81F. That means at the inlet of your server rack you can go to 81 degrees -- that's pretty warm. [The standard also sets recommendation on humidity levels as well.]

What made it possible to change the recommendation? 

It took a year-and-half of all the IT manufacturers talking through this and making sure we had what we felt was some hard data behind this that would meet the new requirements.

Since this standard went out one year ago, what's been the adoption of it? 

Some are starting to use it. We [IBM] are starting to internally use it. It's something that's not going to happen overnight. They [data center managers] will probably step it up two degrees at a time. The benefit will be contingent on an analysis for that data center on what happens if you raise the air temperature and thereby raise the chilled water temperature by "x" amount. Raising the temperature allows you to possibly to turn off the chiller for a longer period time and use outside ambient air to cool your data center. In general, it's like raising the thermostat in your house.

Do you feel is the 81 is a conservative upper recommended limit? 

Above about 77 degrees we all start to speed up our [equipment] fans as the temperature gets higher in order to keep the silicon at a pretty level temperature. We don't want the chip temperature to be jerked around. As the temperature in the inlet into the rack goes up we speed up the blowers to increase the heat transfer, if you will, and to keep that silicon kind of constant. If you start to raise temperature more and more, the blowers and fans speed up more and more, using more power. This is not good. We feel the power increase is minimal for that level, but we did feel that raising it higher than that [the recommended limit] may end up diminishing returns for saving power at the whole data center level.

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