"Again, wrong. RHEL 5 ships with Xen, and will support Xen until at least 2014. OUL also ships with Xen. Please remember, KVM has not shipped in *any* RHEL release (major or minor) yet. Only Red Hat internally knows the release agenda."
I hate to correct an otherwise good post, but that is at best misleading, and at worst just plain wrong. Redhat has announced that they are only going to support existing Xen installations, while providing a way to migrate to KVM.
Xen is dead with Redhat. At least for now.
Personally, I think this is a major screwup by RH, as I know of sites which had been stongly RH but are now looking at dropping them. Sorry, KVM just isn't ready for serious primetime. What's worse, is that the majority of Virtualization research out there is centered around Xen, for the simple fact that it's been around longer.
So Xen is the focus of the next generation of technology, and will remain that way for a while.
And before the KVM fanatics jump up shouting the usual "but-it's-faster!" mantra, you should be aware that Type II hypervisor support (ala KVM) was announced a couple weeks ago at the Xen Summit (at Oracle's HQ, btw).
So one can either choose a KVM type of hypervisor, or the original Xen hypervisor.
Oh, and I heard that the guy who did it coded up in 12 days as a lark.
But unfortunately one doesn't seem to have a choice with Redhat..
I certainly hope CentOS picks up the Xen work from Fedora this year. Otherwise I'll have to look to Oracle for serious datacenter work. I'm not happy about that at all, as I've been a very strong fan of Redhat (and have given them lots of business.
But this really underscores how good it is sticking with Open Source. At least I DO have choices.