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Guest View: Is PUE killing your competitive edge?

Mike Jansma | Jan. 6, 2014
Those who only quote their PUE will be missing a trick in a competitive situation as they'll clearly be under - or over-selling their data centre's performance.

Data is big business, with the data centre market in Singapore expected to be worth some S$685 million by 20171. Energy is big business, worth S$9.7 billion in Singapore2. As energy prices continue to rise and demands grow exponentially on IT, it's vital that data centre managers use both energy and data to their advantage to ensure their facility is the most competitive on the marketplace. Unfortunately, though many think that this is exactly what they're doing, they're wrong. They're being misled by metrics.

Those who strive to make their data centre as efficient as possible will not only combat the environmental impact of an increasingly IT reliant world, but will also enable them to pass significant energy savings onto their customers, turning them into a more attractive prospect than their less energy efficient rivals.

In their quest to become as energy efficient as possible, data centre managers are desperate for measurements that can effectively differentiate them from competitors. The metric used most often by data centre managers keen to brag about their energy efficiency is Power Usage Effectiveness (PUE). Invented in 2007 by the Green Grid, PUE is the ratio of total amount of power used by a computer data centre facility to the power delivered to computing equipment, and can be calculated using this equation:

While a useful measurement tool, a PUE calculation should never be quoted in isolation as an accurate illustration of a data centre's overall energy usage. Differences in how and when power is recorded can cause large fluctuations in the accuracy of the PUE measurement.  Further, the PUE measurement fails to recognize data centre energy efficiency improvements that may reduce total energy use, but actually raise the facility PUE.  Therefore, PUE is a useful tool for facilities managers, but shouldn't be the only way in which performance is measured in those data centres that want to remain competitive.

Glaring oversights

Data centre managers are being blindly driven by the belief that PUE is the magic metric. It's not. It's useful, but only when used in combination with other factors to measure performance.

To illustrate how glaring oversights in using PUE are made, take a look at a data centre that has 1,000 servers, but is only actively using 100 of those. So, to improve energy efficiency a data centre manager would be wise to turn off those additional unused 900 servers. In doing so a data centre manager unquestionably makes their data centre more energy efficient, but the PUE will go up, and by quite a lot, because the power being used is now comparative to 100 servers, rather than 1,000. 

Studies by McKinsey & Co and Gartner Research revealed recently that a mere six to twelve per cent of the electricity consumed by most data centres is used to perform useful IT computations. It would seem that many data centres are responding to demands for service reliability and security by diverting electricity to ensure availability of idle servers in fear of unforeseen downtime. Each of them will be able to show a very good PUE measurement, but the environmental wastage of using electricity to power unnecessary equipment should be unacceptable in the modern competitive market.


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