With technologies such as increasingly placing redundancy into the software layer, the notion of hardware resiliency is starting to become less relevant, reducing the risk of over-heating.

Server virtualization also imposes new power and cooling challenges, however, because hypervisors allow each server to utilize much greater percentages of CPU capacity. On one hand, server virtualization lets IT shops consolidate onto fewer servers, but the remaining machines end up doing more work and need a greater amount of cold air delivered to a smaller physical area.

If you're shutting off lots of servers, a data center has to be reconfigured to prevent cooling from being directed to empty space, Simonelli notes.

“The need to consider power and cooling alongside virtualization is becoming more and more important,” he says. “If you just virtualize, but don’t alter your infrastructure, you tend to be less efficient than you could be.”

Enterprises need monitoring tools to understand how power needs change as virtual servers move from one physical host to another. Before virtualization, a critical application might sit on a certain server in a certain rack, with two dedicated power feeds, Simonelli notes. With live migration tools, a VM could move from a server with fully redundant power and cooling supplies to a server with something less than that, so visibility into power and cooling is more important than ever.The ability to move virtual machines at will means “that technology is becoming disconnected from where you have appropriate power and cooling capacity,” Simonelli says.