Along with the other updates Virtual Iron, Inc. plans to ship at the end of this month is a feature designed to conserve electricity by moving virtual machines onto a small part of a server farm and power down the rest. The software, LivePower, is designed to monitor CPU capacity on the servers running Virtual Iron's server virtualization software and shift virtual machines from one to another to increase the efficiency of the whole group.But instead of ordinary load balancing\u2014which is designed to make the most efficient use of all the available servers\u2014LivePower shifts virtual machines around in order to consolidate as many as possible onto a small number of servers, and power down the rest. The small- and mid-sized companies that are Virtual Iron's target market are, like larger companies, increasingly concerned with the amount of electricity their server farms and data centers are using, according to Tim Walsh, director of corporate marketing for Virtual Iron. Being able to shut down underused servers according to pre-set policies\u2014at night or on weekends, for example\u2014will allow customers to reduce their power use according to schedules and criteria they set themselves. Server virtualization has been pretty successful at reducing the number of servers a company needs and there's no reason the same principle can't be extended to reducing the amount of power those machines use, according to analyst Mark Bowker of Enterprise Strategy Group. "For power-constrained data centers, and we've talked to a few clients who are worried about breaking things because they're pushing the limits of their power so hard, there is definitely some value in it," Bowker says. "But for just a server farm, where you're talking about tens or hundreds of nodes, there's not as much value as there would be with a desktop virtual infrastructure, where you might be talking about thousands of nodes that could be shut down overnight when they're not being used."Virtual Iron is not yet recommending that customers use LivePower on production servers, according to Chris Barclay, product manager for Virtual Iron. The company lists its status as "experimental," and recommends customers use it for development or test environments, at least for the next three to six months.LivePower is tentatively certified on all the hardware for which Virtual Iron is certified, and has completed beta testing. It won't fully endorse the feature for production servers until it gets feedback from customers on how well it performs on a wider variety of server, he says. VMware also offers a power-conserving option calledDistributed 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\u2014and the increasing reliability of the servers on which they run\u2014makes 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.