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Updated 10:00 AM March 9, 2009
 

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PowerNap plan could save 75 percent of data center energy

Putting idle servers to sleep when they're not in use is part of researchers' plan to save up to 75 percent of the energy that power-hungry computer data centers consume.

Data centers, which are central to the nation's cyberinfrastructure, house computing, networking and storage equipment. Each time you make an ATM withdrawal, search the Internet or make a cell phone call, your request is routed through a data center. Government, medical and corporate entities alike use them to store and process information.

Thomas Wenisch, an assistant professor in the Department of Electrical Engineering and Computer Science, and students David Meisner and Brian Gold will present a paper called "PowerNap: Eliminating Server Idle Power" about improving the energy efficiency of data center computer systems on March 10 at the International Conference on Architectural Support for Programming Languages and Operating Systems in Washington, D.C.

Wenisch and the students analyzed data center workloads and power consumption and used mathematical modeling to develop their approach.

The approach includes PowerNap, the plan to put idle servers to sleep, and a more efficient power supplying technique, Redundant Array for Inexpensive Load Sharing (RAILS).

The Environmental Protection Agency expects the energy consumption of the nation's data centers to exceed 100 billion kilowatt hours by 2011, for an annual electricity cost of $7.4 billion. Those figures are about twice what they were in 2006, when data centers already drew more electricity than all the nation's color televisions, or 5.8 million U.S. households.

While PowerNap would require a new operating system to coordinate the instantaneous sleeping and waking of servers, most of the other technologies that would make this possible already exist, Wenisch says.

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, Wenisch says. Idle servers still consume about 60 percent of their peak power draw. And because servers are mostly idle, significant energy is wasted in these power supplies.

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.

David Meisner, first author of the paper, is a doctoral student in the Division of Computer Science and Engineering. Brian Gold, a co-author of the paper, is a doctoral student in electrical and computer engineering at Carnegie Mellon University.

U-M has filed for patent protection on the technology, and currently seeks an industry partner to help bring the technology to market.

Simple data center and server initiatives underway at the University are reducing computing energy levels by 10 percent, which equals $500,000 annually, says Tim Slottow, executive vice president and chief financial officer.

"Green computing is a wide-open environmental frontier and through Climate Savers Computing Initiative, the University is implementing data center and server green computing best practices. More sophisticated solutions such as PowerNap and RAILS could exponentially increase our energy savings," Slottow says.

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