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Group agrees global metric for datacentre efficiency

The EU, the US, Japan and the Green Grid industry group want to use PUE as an international metric for gauging and comparing energy efficiency
Written by Richard Thurston, Contributor

IT professionals are set to benefit from the use of a single metric to measure datacentre efficiency, after organisations from Europe, Japan and the US agreed to work together on a global framework.

The agreement, announced on Tuesday, was reached by the EU Code of Conduct, the US's Department of Energy and Environmental Protection Agency and Japan's Ministry of Economy, Trade and Industry, along with the Green Grid — a datacentre industry consortium that includes heavyweights like HP, Dell, Intel and Microsoft.

"The ultimate goal is to create a set of globally accepted metrics for datacentre energy efficiency," said Tom Brey, secretary of the Green Grid, in a statement. 

The deal sets up the use of power-usage effectiveness (PUE) as the preferred industry metric. PUE measures the proportion of datacentre power that is attributable to IT equipment, and it shows the percentage of energy that is lost to non-productive activities such as cooling and lighting.

The Green Grid believes that PUE can be used to benchmark the energy efficiency of one datacentre against another.

"One of the biggest problems is how you compare one company's datacentres versus another's, and whether they are moving in the right direction on energy efficiency," Alan Priestley, a member of the Green Grid's EMEA technical working group, told ZDNet UK on Tuesday.

"Once you've reported the PUE value, you can make comparisons across datacentres. What we're looking at here is getting an agreement among the various bodies of standardisation for an initial metric, so we've got a consistent set of metrics to report the energy efficiency of the datacentre," Priestley said.

However, Liam Newcombe, co-founder of the datacentre special interest group at the British Computer Society, argued that there can be no "magic number" for datacentre efficiency.

"We can't have one overall datacentre metric," said Newcombe, speaking to ZDNet UK on Tuesday.

Instead, Newcombe proposed a set of metrics that varied by vertical sector that could include the number of web pages served, or processor utilisation, for example. He argued that PUE is problematic because the rating is made worse by implementing power management and could be made worse by virtualisation, both of which often have a positive impact on an organisation. That leads PUE to be irrelevant for many businesses, he said.

Priestley acknowledged the limitations of PUE and said it was important to understand the energy impact of everything in a datacentre. "PUE is not a constant value. A lot of things can affect PUE, so it's important to have the whole datacentre instrumented. This [the development of metrics from the consortium] is still a work in progress."

Green Grid is planning a number of further developments for the consortium. It believes that a measure of the productivity of the datacentre should be next — which would measure the energy efficiency relative to the workload undertaken by the IT equipment. It also wants to make its metrics more granular by breaking down the PUE figure into its contributing factors. Furthermore, it also wants to define energy efficiency guidelines for datacentre components, such as UPS, switches, servers, storage, refrigeration units, generators and power equipment.

The group also proposes defining metrics by individual rack, as organisations start to increase their use of cooling solutions for individual racks in the datacentre.

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