[CentOS] XEN or KVM - performance/stability/security?

Fri May 11 22:46:43 UTC 2012
Gordon Messmer <yinyang at eburg.com>

A late reply, but hopefully a useful set of feedback for the archives:

On 04/20/2012 05:59 AM, Rafał Radecki wrote:
> Key factors from my opint of view are:
> - stability (which one runs more smoothly on CentOS?)

I found that xenconsoled could frequently crash in Xen dom0, and that 
guests would be unable to reboot until it was fixed.  I also found that 
paravirt CentOS domUs would not boot if they were updated before the 
dom0.  In short, Xen paravirt was very fragile and troublesome.  I never 
tested Xen with hardware virtualization.

I have had no such problems with KVM.  In my experience KVM is much more 
stable than Xen paravirtualization.  Xen HVM probably would suffer at 
least some of the same problems.

> - performance (XEN PV/HVM(with or without pv drivers) vs KVM HVM(with or
> without pv drivers))

PV drivers will make some difference, but the biggest performance 
difference you'll see is probably the difference between file-backed VMs 
and LVM-backed VMs.  File-backed VMs are extremely slow.  Whichever 
system you choose, use LVMs as the backing for your guests.

> - security

There have been bugs that allow guests to escalate privileges and access 
host resources, but they're relatively few.  I don't think there's a 
significant difference between the two in this area.

Overall I advise the use of KVM.  It should be more stable, and has the 
advantage of Red Hat support.