VMware also offers a power-conserving option called Distributed Power Management with its suite of server virtualization applications. It is also listed as experimental, or at least not fully supported for commercial environments, and carries warnings about how to manage wake-on-LAN and other automated power up/power-down procedures.

Some data-center managers may be nervous about running servers at low power levels, or shutting them down altogether, then expecting them to power up automatically the next morning, or when traffic picks up again, he says.

But the ability of Virtual Iron and competitor VMware to migrate virtual machines from one physical server to another—and the increasing reliability of the servers on which they run—makes that concern if not obsolete, then at least less dire than it might have been five years ago.

Most of the servers running underneath VMs are commodity level blade or rack-mounted servers, not the fussy higher-end servers that tend to be most at risk during power up/power down sequences. And with a virtual infrastructure, data center managers aren't constrained by the limits of the hardware; they can bypass glitch servers and move already-running VMs onto more units that power up more smoothly.

LivePower will ship as part of Virtual Iron version 4.4, which will be available at the end of this month at no additional cost beyond that of the rest of the software.

© 2009 CXO Media Inc.