Don’t let PUE kill your competitive edge, warns Enlogic

With competition and demand for data centre space heating up, intelligent PDU provider Enlogic is calling for data centre managers (DCMs) to seriously re-consider how they measure energy consumption to avoid overpaying on CRC (Carbon Reduction Commitment) bills.

PUE (Power Usage Effectiveness) has become a commonly used metric for data centre managers to monitor energy efficiency, but when quoted in isolation it can often portray a misleading picture of a data centre’s overall energy usage.

Enlogic is now calling for companies to stop using PUE alone but in combination with more modern solutions, like intelligent PDUs, and performance-related metrics to accurately measure energy consumption and enable real energy consumption savings initiatives.

“Achieving success in a competitive market place is about finding efficiencies and optimising operational costs,” says Mike Jansma, Co-founder and Chief Marketing Officer of Enlogic. “For years data centre managers have been convinced that PUE is the magical metric that will give them this competitive edge – but it’s not.”

Invented in 2007 by the Green Grid, PUE is calculated against the ratio of the total amount of power used by a data centre facility (including lighting, heating, cooling) divided by the power delivered to computing equipment. While PUE does provide an effectiveness metric of the facility services to the IT equipment; it does not provide any meaning in relation to IT equipment efficiency, and in fact can become quite misleading.

“Take an extreme example; imagine a data centre full of thousands of computer servers sitting idle, but consuming energy. Suppose such a data centre has a well-managed facility with a PUE of 1.4; would one believe this is an efficient date centre despite no computing work being done?” continues Jansma.

“In the more realistic situation, PUE can mis-lead users into making poor decisions. For example, suppose an existing data centre consolidates their equipment and shuts down idle servers in an effort to save energy. In this situation, PUE will often increase after the change since the reduced IT energy use does not typically reduce the total facility energy by the same percentage. In effect, the energy use is lower, but the PUE can be higher.”
While reducing total energy consumption is ultimately more important than reducing the PUE, many managers are setting their individual and facility performance goals based on improved PUE, not necessarily reduced energy which is harder to quantify. If key decision makers base their decisions on PUE alone, it could mean paying considerably more than necessary for energy and carbon taxes, despite best intentions to improve carbon efficiency.

Jansma concludes: “The potential energy and financial savings that data centres could achieve are entirely overlooked when PUE is used as a single efficiency metric. The most energy efficient data centres are actually reducing overall energy consumption and costs by looking holistically at PUE in conjunction with IT performance per watt type metrics.”

Enlogic’s intelligent range of energy metering PDUs and environmental sensors actively monitor the data centre environment to enable data centre performance optimization efforts and improve system availability. A small but vital part of the energy supply chain, the Enlogic PDU provides data centre and facilities managers with the intelligence needed to efficiently utilise power resources within the rack and keep track of energy usage.