This is the distribution that is suppose to have Xen embedded into the OS as opposed to just available as a package. It holds some promise if you believe what Redhat is saying about it. 100ms switch times is pretty impressive if it is true. For those of you who are experienced in clustering, you know the complexity that can be involved. Bringing up the whole OS container somewhere in 100ms is fast and less prone to error than traditional active/passive clustering.