For years, Xen and VMware have been the virtualization technologies of choice for open source operating systems vendors. With Red Hat's acquisition of Qumranet yesterday and its competing Kernel-based Virtual Machine (KVM) open source hypervisor the winds of change may be blowing, or not.

While Red Hat is now betting at least $107 million that KVM is the future of virtualization, other vendors in the open source virtualization space aren't so sure.

Red Hat executives claim that it's not a hypervisor war, and that they are now engaged in a battle with only one other vendor that has an end to end platform, namely Microsoft. Among those that participate in the open source virtualization market, Citrix, Sun, Novell, VMware and Oracle all have a stake and few agree with Red Hat's vision.

Simon Crosby, the CTO of Citrix's virtualization and management division in particular has some harsh views on Red Hat's virtualization market positioning. In his view, Red Hat is an OS vendor and their direct competitors are other OS vendors like Novell and Oracle on the Linux side and Microsoft on the Windows side.

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