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

Pasi Kärkkäinen

pasik at iki.fi
Tue Jun 5 06:36:36 UTC 2012

On Fri, May 11, 2012 at 03:46:43PM -0700, Gordon Messmer wrote:
> A late reply, but hopefully a useful set of feedback for the archives:
> On 04/20/2012 05:59 AM, Rafa?? 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.

This was a problem in RHEL5/CentOS5 Xen. It was fixed in upstream Xen years ago.
I think it was fixed finally in RHEL5/CentOS5 Xen in 5.7 or 5.8.

The workaround was to simply kill+restart xenconsoled. No reboot required.
Also I think the xenconsoled bug only happened on 32bit hosts.

>  In short, Xen paravirt was very fragile and troublesome.  I never 
> tested Xen with hardware virtualization.

Xen PV has been rock solid for me :)

> 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.

You should compare Xen HVM with KVM, and you said you haven't been running Xen HVM.

> 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.

Xen is supported by Red Hat support in RHEL5.

-- Pasi

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