Well it seems that I’m not the only one that’s concerned about how we measure data centre energy efficiency (see my comments yesterday).
On Google’s Public Policy blog, Urs Hoelzle, Senior Vice President, Operations and Google Fellow, posted a comment on Monday criticising the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) for its prescriptive standards for data centres. It’s not just a Google comment, though, it’s an open letter from senior executives at a number of prominent IT companies and data centre operators, including Digital Realty Trust, Dupont Fabros Technology, Amazon, Nokia and Microsoft.
It seems that the ASHRAE has recently added data centres to its building efficiency standard. The standard defines the energy efficiency for most types of buildings in America and is often incorporated into building codes across the country.
Google and the others feel that the proposed standard is too prescriptive because it dictates which types of cooling methods must be used. For example, it requires data centres to use economizers — systems that use ambient air for cooling. We’ve reported in the past how effective it can be to use available air for cooling, but, as Google points out, requiring their use doesn’t guarantee an efficient result. In any case, they may not be the best solution and future cooling methods may be even better.
The point being made by Google and the other signatories is that in data centres, where the energy used is easily measured, for cooling for example, a standard should set the required efficiency without prescribing the specific technologies to accomplish that goal. (The letter points out that, in the case of car fuel efficiency, standards specify how much gas/petrol a car can consume per mile but not what engine to use).
Google points out that data centre industry leaders have already agreed that Power Usage Effectiveness (PUE) is the preferred metric for measuring efficiency and that the EPA Energy Star program already uses this method.
This seems like a collision between a fast moving, international technology sector and a much more slowly developing national building industry. Both are trying to ensure energy efficiency but from very different perspectives.
My first thought is that many major IT companies and data centre operators have already made extensive efforts to increase efficiency in data centres, with significant success. Anyone reading my comments over the last couple of years will know of the leapfrogging between companies to see who has the greenest data centre. If you introduce a prescriptive standard then that may well become a limiting factor. And what about re-fits? I assume the standards only address new data centres, but many are being re-fitted to be more energy efficient.
But my main reason for supporting Google et al is that I want to see transparent, globally agreed, comparable standards employed, such as those now being developed by The Green Grid. That’s the only way that real comparisons can be made enabling companies to be judged and customers to make informed choices.