[CentOS] upgrading Centos-Xen when version 6 comes along

Wed Nov 17 16:38:43 UTC 2010
Paul Heinlein <heinlein at madboa.com>

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 

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.

Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/