On Wed, 17 Nov 2010, Rudi Ahlers wrote:
Have anyone used both XEN & KVM before? What are your experiences with either, in comparison to each other? We've been using XEN for about 4 years now, and only use CentOS as our server platform. I'd hate to move to Debian or OpenSuse just for XEN, and I don't know KVM at all.
We run both Xen and KVM under CentOS 5 (on separate machines, of course) and I haven't been able to spot significant performance differences between the two.
RHEL 6 is supposed to contain a Xen-to-KVM migration tool, but I haven't seen it in action.
It took me a while to figure out the KVM/libvirt XML configuration files; some cookbook-style documentation for them would be a great gift!
The biggest single up-front difference for me on CentOS machines was that KVM hosts default to NAT on a private bridge while Xen hosts default to straight bridging. Some network tweaks are necessary to get KVM hosts to live on a straight bridge.
Also, if you assign MACs to your VMs at installation time (I do, for DHCP- and DNS-related reasons), you should note that KVM MACs lives in a different namespace: 54:52:00:xx:xx:xx.
I haven't done host migration with Xen, but it works quite well with KVM -- once you have the shared storage and security mechanisms configured properly.