'Power Naps' for Data Centers Offer Major Energy Savings: Researchers

Published March 09, 2009

How fast can your server go to sleep? And perhaps more importantly, how quickly can it wake up?

If you can get your machines to snooze for the few hundred milliseconds at a time when it's not in use -- and then wake up in time for the even shorter dozens of milliseconds when it is needed -- then you're in the running to save as much as 75 percent of the energy used by your data center.

Those are the findings of a paper released today by two researchers at the University of Michigan. Two students in the Department of Electrical Engineering and Computer Science at the University of Michigan, David Meisner and Brian Gold, are releasing their PowerNap study along with assistant professor Thomas Wenisch at the International Conference on Architectural Support for Programming Languages and Operating Systems in Washington, D.C.

PowerNap is a catchy name to explain the new theory developed by the researchers, and the technology that backs it up.

Excessive power use is one of the biggest problems facing data centers today: in addition to causing skyrocking energy bills, studies have found that significant numbers of data center managers expect to hit the limit of the power available to their facilities in the near future.

In studying the power used by 600 servers, the researchers found that machines on average idle for hundreds of milliseconds at a time, and then undergo a burst of activity lasting just tens of milliseconds. The result is much higher energy use than is needed.

"For the typical industrial data center, the average utilization is 20 to 30 percent. The computers are spending about four-fifths of their time doing nothing," Wenisch said in a statement. "And the way we build these computers today, they're still using 60 percent of peak power even when they're doing nothing."

To address the issue, Wenisch and his partners in the study are proposing PowerNap, a system to take systems offline extremely quickly, and wake them up even more quickly, as a way of conserving energy at a very high level. And while a system like PowerNap would require a new type of operating system to manage, the more challenging component is developing a new power supply that can meet these needs.

In their presentation at the confernce, Wenisch and his students are also unveiling RAILS (Redundant Array for Inexpensive Load Sharing), a power supply technique that can provide energy at such quick bursts.

In an example from the paper, the authors propose a new way to power a rack of blade servers. Rather than a single 2,250-watt power supply, RAILS would use a larger number of 500-watt systems that could power the servers as needed and cut down on power loss.

The University has already filed a patent on the technology and has said it is looking for a business partner to bring PowerNap and RAILS to market.

Blade server photos CC-licensed by Flickr users jjvaca and tom_twinhelix.

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'Power Naps' for Data Centers Offer Major Energy Savings: Researchers

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