Linode, a 15-employee company that operates five data centers between the U.S. and the U.K., has come to rely on automation built in-house around the open source Xen project. However, recent updates made to open source Xen -- to keep it current with the latest Linux kernel -- have not tested well in Linode's environment, said Christopher Aker, founder and CEO of the Absecon, N.J.-based company.

"The first few machines worked, but you get 20 to 30 machines in and it's a different story," he said. "I don't trust the initial build. We have to let things cook."

Linode already shifted platforms once, from user-mode Linux to Xen, and has kept Xen stable "just with elbow grease and trial and error," Aker said.

"It's premature to say let's bet the farm on KVM," Aker said. "I think Xen is going to reach a critical point where it moves off its old domain zero, or it will obsolete itself. If that happens, KVM would be a likely substitute out of necessity, but Linode has paid its [platform migration] dues. We're going to let someone else pay those dues this time."