Microsoft: Green IT Means More Than a Low PUE

Microsoft: Green IT Means More Than a Low PUE

Power Usage Effectiveness has become the de facto standard for green IT around the world, but a new white paper from Microsoft says that PUE shouldn't be the only focus of an IT department.

PUE -- the ratio of a data center's energy use that goes to computing instead of HVAC or lighting -- was developed by The Green Grid to move the IT industry toward more efficient operations. But according to Dileep Bhandarkar, a Distinguished Engineer in Microsoft's (NASDAQ: MSFT) Global Foundation Services, PUEs can be a misleading figure because it is inconsistenly reported.

In the white paper, Bhandarkar lays out some "non-intuitive" changes that Microsoft made to one of its sites over a three-year period, including painting the roof white and improving air flow by shifting concrete walls around AC units. Those changes, along with other projects, led to a 25 percent reduction in the site's PUE over the course of three years.

But, Bhandarkar writes, "just improving PUE should not be an organization's goal. The real goal is to eliminate waste and pack as much compute capability in the available power budget. PUE can be a useful indicator of energy efficiency, but it can also mislead you if used blindly. Take for example a scenario in which the fans in a server can be removed without impacting its performance. The elimination of fan power reduces the IT power (fan power is part of IT power), improves energy efficiency, but it also increases the PUE!"

The white paper also lays out some of Microsoft's green data center strategies and its goals going forward. Bhandarkar writes about the company's Chicago data center, which used containerized data centers (pictured above left) to maximize compute power while remaining within an already-allocated power budget.

The results -- with a PUE of 1.2, down from the company's worldwide average of 1.6 -- point the way to Microsoft's future data center plans. Bhandarkar describes container-based systems as "a useful tool." Also included in Microsoft's green data center toolkit are a range of technologies, depending on what is most appropriate for the location, including air-side economization (as the company used in Dublin, Ireland), free outside air cooling, and water-cooled systems.

"Microsoft views its future datacenters as driving a paradigm shift away from traditional monolithic raised floor mega datacenters," Bandharkar writes. "Using modular pre-manufactured components yields improvements in cost and schedule. The modular approach reduces the initial capital investment and allows you to scale capacity with business demand in a timely manner."

Over the last several years, the company has unveiled a number of hints as to its future data center plans, including plans released in late 2008 for a modular, scalable and super efficient data center and a "purpose built" data lab in Redmond.

The full white paper, "A Holistic Approach to Energy Efficiency in Datacenters," is available for download from