Quoting from eWeek:
Red Hat’s announcement March 14 of its integrated virtualization push, starring Xen, didn’t take anyone by surprise: Red Hat, along with just about everybody else, has been tooting the Xen horn ever since the fledgling open-source virtualization technology began grabbing headlines almost a year ago.
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The trouble is that Xen is somewhat early on in its development, and the high rate of change in Xen’s code base will keep the technology out of the mainstream Linux kernel for some time.Red Hat has and will continue to chart its own course with respect to the kernel, diverging from the mainstream where and when appropriate, but Xen’s potential will remain somewhat stunted for as long as it remains in heavy flux…
Read the whole article at source.