March 13, 2009 The average utilization for a typical industrial data center is as low as 20 to 30 percent - and the computers are still using 60 percent of peak power even when they're doing nothing. To combat this problem, researchers at the University of Michigan have put together an approach that could save up to 75 percent of the energy that power-hungry computer data centers consume.
The approach, developed by Thomas Wenisch, assistant professor in the Electrical Engineering and Computer Science and students David Meisner and Brian Gold, includes PowerNap, an energy-saving plan to put idle servers to sleep, and a technique dubbed Redundant Array for Inexpensive Load Sharing (RAILS), which supplies power more efficiently.
Techniques employed today such as dynamic frequency and voltage scaling don't do enough to conserve power, the researchers say. PowerNap would enable servers to sleep periodically like ordinary laptops. However, they would have to slumber and wake exceedingly fast, Wenisch says.
While PowerNap would require a new operating system to coordinate the instantaneous sleeping and waking, most of the other technologies that would make this possible already exist.
"There aren't really technological barriers to achieving this," Wenisch said. "The individual components know how to go to sleep fast. Engineers have developed that technology for laptops and smart phones. But the pieces haven't been used in servers where you don't have a user closing the lid. The components are out there, but the system needs to be redesigned."
While the computer parts might not be hard to find, the power supply would need to be overhauled for PowerNap to work properly, the researchers say. Their new RAILS technique addresses this problem.
Today's power supply technique for stacking blade-based servers connects about 16 computers to a handful of 2,250-watt power supplies. The arrangement is inefficient unless the machines are running full steam.
To cut down on the power loss, RAILS would replace the one 2,250-watt power supply with a bunch of smaller, 500-watt power supplies. RAILS would be a necessary complement to PowerNap because without it, even sleeping servers would waste energy.
"Together, these approaches can help make data centers green and solve these big energy efficiency challenges," Wenisch said.
Wenisch and his team presented their paper PowerNap: Eliminating Server Idle Power on March 10 at the International Conference on Architectural Support for Programming Languages and Operating Systems in Washington, D.C.
Karen Sprey