This week, the New York Times ran a series of articles about data center power use (and abuse) “Power, Pollution and the Internet” (http://nyti.ms/Ojd9BV) and “Data Barns in a Farm Town, Gobbling Power and Flexing Muscle” (http://nyti.ms/RQDb0a). Among the claims made in the articles were that data centers were “only using 6 to 12 % of the energy powering their servers to deliver useful computation. Like a lot of media broadsides, the reality is more complex than the dramatic claims made in these articles. Technically they are correct in claiming that of the electricity going to a server, only a very small fraction is used to perform useful work, but this dramatic claim is not a fair representation of the overall efficiency picture. The Times analysis fails to take into consideration that not all of the power in the data center goes to servers, so the claim of 6% efficiency of the servers is not representative of the real operational efficiency of the complete data center.
On the other hand, while I think the Times chooses drama over even-keeled reporting, the actual picture for even a well-run data center is not as good as its proponents would claim. Consider:
A new data center with a PUE of 1.2 (very efficient), with 83% of the power going to IT workloads.
Then assume that 60% of the remaining power goes to servers (storage and network get the rest), for a net of almost 50% of the power going into servers. If the servers are running at an average utilization of 10%, then only 10% of 50%, or 5% of the power is actually going to real IT processing. Of course, the real "IT number" is the server + plus storage + network, so depending on how you account for them, the IT usage could be as high as 38% (.83*.4 + .05).