Electricity used for cooling accounts for one third and sometimes even half of the total electricity bill. For a datacenter of about 3.000 m² and consuming about 10 MW, the electricity cost for cooling your datacenter may rise up to 3 to 6 million euro, according to the calculations by a research team in the university of Toronto made less than a year ago.
Research of the Department of Computer Science – University of Toronto

This same research team has investigated what would be the effect on the system reliability if you would raise the temperature by some degrees, a measure that could lead to considerable cost savings on the electricity bill.

The results are quite revealing. Without going into too much detail, the effects of turning up the temperature by several degrees are far less than generally assumed. There is little or no correlation between higher temperatures and DRAM failures or node outages. And the correlation between higher temperatures on the one hand and latent sector errors in disks and disk failures on the other are far weaker than expected.

What seemed to impact the hardware reliability far more, however, were huge variances in temperature. So rather than keeping the temperature as low as possible, datadenter operators should strive to keep the datacenter temperature as consistent as possible.

Does this mean that one can allow the temperature to rise up to 50° Celsius or more? Not exactly, because a rising temperature would lead to a dramatic increase of the power consumption of individual servers, if only because of the increasing fan speed of these servers. That way, the positive effect of a lower cost of cooling in general would be neutralized by the higher cost of the servers’ power consumption.

But the results do indicate that the average datacenter temperature may well be turned up a few degrees and the monitoring efforts should focus more on keeping the temperature constant than on keeping it low. By the way: too low temperatures are harmful to your hardware as well.

The scientists were reluctant to provide specific advice on ideal datacenter temperatures, but they did find the results encouraging and worth some further investigation.

Up to recently, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommended an inlet temperature range of 18 to 27 degrees Celsius as a safe temperature without damaging the equipment, but if the above research is confirmed, the recommended range may be expanded significantly.

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