Tonight I’ve been reading a commentary about green data centers. While I can’t fault most of the recommendations, I think the definition of green-ness is way off base.
Any measurement that attempts to define a data center as green or not green without taking into account the amount of work achieved by that facility is worthless. I’ve taken the Green Grid’s PUE (power usage effectiveness) and the EPAs EUE (energy usage effectiveness) both to task for this. Now I include blanket negative mentions of a facilities carbon footprint.
The problem is that none of these measurements tell you anything about how efficiently a data center uses the energy it consumes to produce useful work. Stating a facility’s carbon footprint without any reference to the work produced by the facility is dishonest as best. The worst part is, without that final piece of the equation, it’s impossible to use any of these metrics to compare different data centers (not that this stops companies from using these as a marketing tool or potential customers from demanding these numbers).
The fact is, data centers can get great looking PUE numbers, have tiny carbon foot prints, and turn out pathetic amounts of work for the energy they consume. Fill a data center with idle servers and I’ll give you a fantastic PUE with ZERO work being done at all! Consuming energy without producing work is NOT in my definition of being green.
Are these metrics totally useless then? Absolutely not. PUE is useful as an internal measurement of cooling efficiency. Improve cooling efficiency, power required to cool goes down, PUE goes down, and that’s a good thing. Carbon footprint can tell us useful things about the energy sources that supply the data center. Replace traditional power sources with green power such as solar or wind (points for power generation on site!) and your carbon footprint goes down for the same amount of useful work, and that’s not a bad thing either.
When it comes right down to it, the only reasonable measurement of efficiency is energy consumed vs work accomplished. You could even expand this to cover the whole system as energy generation efficiency vs energy delivery efficiency vs energy consumed vs work produced to cover everything from the utility power generator to the output of the data center. Now you have something that can be used to compare different data centers, apples to apples. This is what the EPAs EUE should have been.
Efficient power generation, efficient delivery, efficient use of the power to produce as much useful work as possible. This is that real definition of a green data center.
Vern, SwiftWater Telecom