In all fairness to the good people over at EPA who have been working with the industry, academia, manufacturers and associations like The Green Grid – they really were stuck between a rock and a hard place when it came to ENERGY STAR for Data Centers. On the one hand you have America’s political bodies telling them they “have to do something” to change the shape of the power consumption curve attributed to data centers in the EPA Report to Congress while at the very same time EPA is working with industry to define a metric, proxy, or group of proxies for work in a data center so we can have a meaningful discussion on IT, and by extrapolation data center, productivity per watt. So they slammed together some of the more typical data requirements of general “building” efficiency, such as energy intensity (kW/square foot), with what can be viewed as the building blocks for data center specific, “nice to know”, data along with some placeholders for a future productivity metric.
All in all not a bad first-pass! When you consider that a large number of data center operators don’t even know how much energy their data centers use a month; EPA’s starting point of knowing and reporting energy consumption certainly makes a lot of sense. In fact, if you did nothing other than identify, monitor, and report your data center’s total energy consumption on a monthly basis and compare that to your IT workloads (applications, bit traffic, storage volume & traffic, VMs, etc.) you are light-years ahead of your peers. And you are now well on your way towards understanding the system-level movers that shape your data center energy use and profile.
Now one area of possible contention in the ENERGY STAR for Data Centers program is the continued reliance on PUE to identify market leaders. PUE is not a measure of productivity and provides only a basic level of useful information to the data center operator. Though we often hear PUE claims bandied about in the market place as if PUE were the ultimate benchmark, it is intended to be used as a tool within each unique data center as an internal reference point. For the most part, much like snowflakes, no two data centers, or for that matter PUEs, are identical.
There are some benefits of knowing your data centers’ PUE, like actually understanding the total energy used by the data center and having a ROM of the total energy consumed by the IT equipment. I say ROM as using the power meter from the UPS in this exercise is far beyond the scope of its intended purpose. Most UPS power meters are at best +/- 5% in accuracy and more often are only +/- 10%. Therefore the closest one can hope to get in reporting PUE is to the tenths, with a corresponding +/- 10% and quite likely +/- 15% degree of system-level precision. So you can forget about reporting a PUE of 1.75! It is meaningless without understanding the accuracy and precision of your meters.
Still, I recall a recent conversation with Alan Mamane, CEO of 42U, where we agreed that PUE is perhaps one of the better starting points the data center industry has available today. That anyone with a PUE above say 2.7, most likely has some low-cost, easy to fix issues that a simple energy efficiency audit would identify. And once you have taken steps to bring the PUE down closer to the national average the EPA has identified, somewhere in the range of 2 – 2.2, it gets a little harder to move PUE significantly as some issues may be endemic to the building itself.
At that point in time one should consider the Energy Logic approach to drive down total energy consumption while building the framework to define and improve data center productivity.
And for those of you who are patiently waiting for an IT productivity metric – stop waiting! Come join the work underway within The Green Grid where they have a fantastic task force (Proxies Task Force) exploring several interesting proxies for IT work. For those already contributing members of The Green Grid this task force is within the Data Center Metrics and Measurements work group. For those not yet members – you can join here.
Disclosure: I am a member of the Board of Directors of The Green Grid.