Server Naps

Server Naps

Programming big computer servers to shut on and off in fractions of a second could save huge amounts of power.


Putting computer servers to sleep. I'm Bob Hirshon and this is Science Update.

Computer data centers, which route digital traffic from the Internet, cell phones, and other devices, are consuming more and more electricity—almost equal to that of 10 million average households by 2011. University of Michigan computer scientist Thomas Wenisch and his colleagues have a solution: put these giant servers to sleep when they're idle, just like a desktop computer. The catch?

There's often less than a second where the computer’s doing nothing, and that's just too short a time to turn computers off using conventional means.

But his team found that a new approach called PowerNap, which actually puts servers to sleep for fractions of a second, can potentially cut their energy use by 75 percent. PowerNap requires replacing a server's operating system and electrical supply, but Wenisch says that's a matter of time and money, not technology. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

“No Internet right now—the server's down.” You may have heard this at school, at the library, or other places with some kind of e-mail or Web access. But what does that mean, exactly? We live in an era when all kinds of devices can “talk” to one another: PCs, laptops, cell phones, electronic organizers, ATM and credit cards, and so on. We use these instruments to send and receive information to and from other devices.

But these instruments don't communicate directly with one another. Just as every letter you send gets routed through a post office—often, several post offices—before it reaches its destination, every electronic exchange gets routed through at least one centralized computer data center. A center may fit in one small room, or take up several entire buildings. Each center is filled with stacks of computer equipment that store data, process incoming and outgoing information, and supply power to the network.

Since the technology boom of the 1990's, data centers have taken up more and more space and energy. As you heard, the Environmental Protection Agency estimates that by 2011, data centers will draw as much power as 10 million average households every year. That's $7.4 billion worth of electricity.

What's more, most of that energy gets wasted. Data centers are designed to handle big surges in electronic traffic—otherwise, all those gizmos we use would be incredibly unreliable, especially when we need them most. As a result, data centers are usually processing much less information than they're capable of handling. But that doesn't translate into an equivalent energy savings: “The computers are spending about four-fifths of their time doing nothing," says Dr. Wenisch. "And the way we build these computers today, they're still using 60 percent of peak power even when they're doing nothing."

For personal computers, it's possible to conserve energy by programming the computer to “sleep” whenever it sits idle for more than a few minutes. When you're dealing with a server, that concept becomes much more challenging. That's because even though servers spend most of their time “doing nothing,” each period of idleness may last for only tenths of a second, punctuated by bursts of activity lasting a few hundredths of a second.

However, Wenisch says a combination of new software, including a program called “PowerNap,” and changes to data centers' power supply, could make such incredibly short naps possible. As with many ecological challenges, the technology is available, and the potential energy savings are large in the long run, but it will take some up-front investment to change today's data centers over to a new system. Now, his team is working on ways to make the change more financially attractive.

Now try and answer these questions:

  1. What is a computer data center? What does it do?
  2. Why have computer data centers become such big consumers of electricity?
  3. How would the PowerNap plan reduce electricity demand?
  4. Can you think of other ecological challenges that may save money in the long run, but are expensive in the short term? How do you think these challenges should be met? 

You may want to check out the March 27, 2009, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: how sleep affects your long-term memory, nap-time for computers saves energy, and how we smell fear in people-literally.

For Educators

How Internet Search Engines Work, by HowStuffWorks, provides a good introduction to the role of servers in a common use of the Web.

The ScienceNetLinks lesson Communications Technologies gives students an understanding of communication technologies and an appreciation of the opportunities and problems that come with these technologies. In the lesson, students try out a few innovative examples of communications technology and learn how they transform patterns of sound or light into patterns of electricity.

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