The Green Grid’s PUE standard is on its way to ISO. Peter Judge wonders what that leaves for IT efficiency warriors to do
The Green Grid must be feeling pleased with itself. Its PUE (power usage effectiveness) idea is on its way to becoming an international standard. Although this begs the question, what’s left for it to do now?
PUE is a simple measure to give an idea how efficient a data centre is, by taking the total power it uses, and dividing it by the amount that reaches the IT systems. The closer it is to one, the better. It’s been widely used and misused to measure and compare how “green” data centres are, and now is reaching an audience outside the IT industry.
The measure has been taken up by a complex-sounding taskforce, mostly comprising US-based bodies such as the EPA, and the output from that discussion has been passed to the formal international standards process. JTC1, the technology committee of ISO, the International Organization for Standardization, looks likely to give it formal approval.
No one is quite sure how long this will take. The Green Grid has optimistically said it could take “months”, but ISO processes are notoriously slow. The likely output will, more or less, be a rubber stamp of what the Green Grid has produced however – coinciding with the ISO move, the Grid has published a formal paper.
“PUE really needs to be a year long average, and users should identify clear boundaries,” said Dave Snelling, vice chair of the EMEA technical committee of the Green Grid, speaking form the Green Grid’s EMEA Forum in Brussels. “We think the standards community will pick that up as advice. It may take three years, and there will probably be some name changes and definitions.”
So what next for the Green Grid? Its flagship measure has now been endorsed, but there is plenty more to do, says Snelling.
For one thing, it needs to address the fact that PUE, much as we love it, isn’t really very good. We have banged on about it here at some length, but while PUE has done a good job of alerting the industry to the amount of energy used outside the IT load, it PUE doesn’t say anything about the use of energy within the IT part of the equation. So some organisations, we are told, are reducing their PUE by unplugging things in the data centre, and finding ways to plug them into the IT system – for instance, running the lights by Power over Ethernet (PoE).
“PUE has worked,” is how Snelling put it. “There’s been a huge move to drive PUE down. Now, the only way to improve is to look within IT”.
The Green Grid isn’t playing any favourites here. Snelling describes work that measures how much useful computing work you get per Watt – but admits that there’s no agreed way to do that yet, because the usefulness of the work is subjective: “A complicated formula for productivity is the ultimate holy grail.”
FVER, the suggested metric from the British Computer Society (BCS), was presented at the Grid’s EMEA Forum, by Gary Thornton and Adrian Jones – but that doesn’t imply any official backing, said Snelling – only that the Grid thinks it is an interesting approach. FVER adds together fixed and variable costs associated with a data centre, where fixed costs are the overhead, and variable costs cut in when the centre is working.
Like PUE, FVER approaches 1 as efficiency increases – in this case because the fixed costs are reduced. But this time the fixed costs in the IT load are combined with those outside.
Plenty more work
The Green Grid has other projects on the go. It has advised IT firms to run their servers hotter, and today made that paper (Data Centre Efficiency and IT Equipment Reliability) more widely available.
It’s also stepping into the territory where you normally find organisations like Greenpeace – considering the overall lifecycle of IT equipment. Every piece of electronics contains embodied energy, uses energy during its lifetime and takes energy to dispose of safely. Similarly, all these processes involve emissions and possible pollution.
There are plenty of organisations working on making a lifecycle model for technology equipment, and the Grid wants to work with them all, to produce a model for the IT lifecycle which can be used elsewhere. There is already an ISO standard (ISO 14040) which defines in really general terms, what should be included and what should be left out: the Grid wants to work with that and make it possible to deliver a comprehensive lifecycle impact for any given piece of IT kit.
So, if PUE becomes a standard, it may leave a gap in the lives of Green Grid members who like to argue about that particular metric. But it seems sure they will find plenty to fill the time.
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