The McKinsey stats quoted show that only 6 – 12% of energy used by data centres actually does any computing and this is not very different from the figures which have been widely accepted in the IT industry for decades. I’ve seen calculations that demonstrate the power that actually gets used doing any “computing” is as low as 2% and you can debate whether it’s now improved to 6% or 12%.
What we all know for sure is that it is low. We all know that most of the power that goes into a data centre gets used along the way, in UPS and air conditioning systems, running the server fans and spinning the disks, and very little is actually used by the processors themselves.
The NYT article ends with a brief comment on “the cloud” and the fact that this will further increase the demand for large, power hungry, data centres, stating: “Some industry experts believe a solution lies in the cloud: centralizing computing among large and well-operated data centres.”
So the question this raises is: “will using the cloud waste less energy than operating your own data centre?”
The advocates of “the cloud” claim, as you would expect, that it will reduce energy use. This claim seems to be based on two premises: firstly, that the large data centres that host your cloud service will be more energy efficient (more efficient servers and better PUE) than your own small one and secondly, that the effect of being able to spread the load among a number of data centres reduces the amount of spare capacity required and therefore of energy wasted.
So let’s take the first of these – is a large data centre necessarily more energy efficient than a small one? The answer is: no.
As far as the servers go, the servers you buy to install in your own data centre are just the same as the ones the cloud providers buy. As for PUE, it is quite possible to build a small data centre with a very good PUE just as it is possible to build a large one with a very poor PUE. The factor which is most likely to affect the energy efficiency of a data centre is not its size but its age and the age of the servers. New servers are much more energy efficient than old ones and any properly designed data centre constructed in the last 3 – 5 years will (or at least should) be vastly more efficient than one built say 8 or 10 years ago.
This brings us to one of the difficulties which the cloud presents for the user – you don’t actually know which data centre is processing your data. So, whereas with old fashioned “hosting” you could audit the data centres you intend to use and verify their energy efficiency, resilience, security etc, now you can’t, or at least not if the cloud works the way its proponents say it does.