In fact, all the parties with whom I spoke noted the potential benefits of reining in energy waste by powering down servers. Cisco, for example, has found that servers in idle state still consume 40 percent of their power. Those wasted watts can add up over time.
Timing is everything
Servers that sit in idle state for long periods of time are the top candidates for powering down between uses. Cassatt's Oestreich pointed to some specific applications that fall into that category. The biggest area for potential savings, he said, is "dev and test where you have a test running for awhile, and then the project's over and you leave the server on and it's doing nothing."
The second biggest area, he said, is failover, "where machines are plugged in and on their entire lifetime, and in theory doing nothing their entire lifetime." A third application could be staging servers, where applications are tested before going live.
Cisco's Aldrich said servers that only perform a single function that can be readily predicted (e.g. scheduled well in advance) are prime candidates for periodic shutdown. That includes batch payroll processing functions, which only take place during pay periods.
IBM's McCredie noted that the practice of shutting down servers could even make sense for applications such as Web hosting as well. "When everybody is at home, Web hosting is fairly modest. When everyone goes home and starts shopping and surfing the Web, Web hosting kicks up.... During the day, you might want to power down some of your server farm, then power them back up when you have heavy use at the end of the day."