In the span of two years -- from 2003 to 2005 -- operating power density in data centers jumped from an average of 25 watts per square foot to 52 watts, says Peter Gross, vice president and general manager at HP Critical Facilities Services. At Industrial Light & Magic, Gary Meyer, systems engineer and project manager, was just finishing up a new data center designed for 200 W per square foot. He wondered openly back in 2005 if the company should have pursued a 400-watt-per-square-foot design instead.
Then the growth curve suddenly slowed as several moderating forces came into play. One was the development and use of better power-management tools. Another dramatic change has been advanced power supplies, which increased in efficiency from a low of 65% to more than 90%, even when utilization levels are low. Another improvement: the adoption of variable-speed fans in everything from servers to computer-room air handlers.