Don’t Use PUE To Compare Data Centres, Says Green Grid

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Efficiency measures such as PUE have raised awareness of the need to curb data centre power, but they aren’t intended to compare one site with another, a summit heard

Data centre efficiency measures developed by the Green Grid have raised awareness of the importance of using less energy – but they should not be used to compare one data centre with another, a virtual conference was told this week.

The vendor-led group has developed PUE (power usage effectiveness) as a way to determine how much of the electricity it consumes, is actually doing computing work. But comparing PUEs between data centres could be misleading, Green Grid leraders told Next Generation Data Center summit, an online event attended by over 600 people.

“PUE is a relational metric,” said Vic Smith, EMEA data centre strategist at Dell, and a senior member of the Green Grid. “It’s not meant to be used as a comparison between data centres”.

PUE doesn’t measure how much productive work is done by the data centres, or their level of availability – for instance, a Tier 4 reliable data centre would have capacity running in idle mode, perhaps using 60 percent as much power as the live equipment. And virtualisation can lower the PUE, while dramatically raising the utilisation of the site, he said.

Despite the limits of PUE, Smith was pleased to see that several operators are now quoting low PUE scores – for instance oil explorer PGS claims a PUE of 1.2 for its data centre in Surrey, and new architectures are emerging.

Between them, Smith and other speakers, from Sun Microsystems, the British Computer Society (BCS) and others presented practical ideas to improve the efficiency of data centres, such as maintaining separation between cold and warm air, and measuring temperature and power close to the servers.

The EU code of conduct on data centres, was covered along with impending carbon reduction regulations.

All the presentations are available online, and further summits are planned.


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