Researchers: Servers Should Sleep Like Laptops

Laptops periodically sleep to conserve power, so researchers ask why not apply the same thinking to servers and cut power usage by 75 percent?

Academics from the University of Michigan are set to announce the findings of research into server power usage this week which applies the same energy conservation thinking that has been used for laptops for decades, to servers.

Thomas Wenisch, assistant professor in the Department of Electrical Engineering and Computer Science, and students David Meisner and Brian Gold, are set to present the research on Tuesday at the International Conference on Architectural Support for Programming Languages and Operating Systems in Washington, D.C.

The research is based around two approaches: PowerNap, a plan to put idle servers to sleep in the same way as laptops, and Redundant Array for Inexpensive Load Sharing (RAILS).

According to Wenisch, data centres waste most of the energy they draw and facilities are inefficient because they must be ready for peak processing demands much higher than the average demand.

“For the typical industrial data centre, the average utilisation is 20 to 30 percent. The computers are spending about four-fifths of their time doing nothing,” Wenisch said. “And the way we build these computers today, they’re still using 60 percent of peak power even when they’re doing nothing.”

Wenisch said his analysis of 600 servers showed that the demands on datacentres are “sporadic and sparse” with the average idle period a mere hundredth of a millisecond and the average busy period just tens of millisecond.

The researches said that the PowerNap technology would require a new operating system to “coordinate the instantaneous sleeping and waking” but most of the other technologies to make it 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.”

On the issue of the RAILS technology, the academics claim current power supply techniques – for example multiple blade servers connected to a handful of 2,250-watt power supplies – are inefficient unless the machines are running at full steam.

To cut down on the power loss, RAILS would replace the one 2,250-watt power supply with a series of smaller, 500-watt power supplies, the researchers claim. “RAILS would be a necessary complement to PowerNap because without it, even sleeping servers would waste energy,” Wenisch said. “Together, these approaches can help make data centres green and solve these big energy efficiency challenges.”