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

On Mon, Apr 23, 2012 at 01:02:03PM -0400, Steve Thompson wrote:
> On Mon, 23 Apr 2012, Peter Peltonen wrote:
> 
> > I've been quite happy with Xen under CentOS5. For CentOS6 the
> > situation is a bit more problematic, as RH switched to KVM and left
> > Xen behind.
> 
> I used Xen for about four or five years before switching to KVM. I like 
> KVM better in every way, and for my fork-heavy workloads, the performance 
> is a lot better than Xen. It is also much easier to use and is in my 
> experience more stable.
> 

with "fork performance" I assume you're comparing Xen PV to KVM ? 

Yes, PV has disadvantage (per design) for that workload, since the hypervisor
needs to check and verify each new process page table, and that has some performance hit.

For good "fork performance" you can use Xen HVM VMs, which will perform well for that workload,
and won't have the mentioned performance hit.

And of course with Xen HVM VMs you should use the Xen PVHVM drivers so the disk/net 
IO paths are optimized and bypassing all the emulation.

CentOS5 and CentOS6 do have Xen PVHVM drivers.

-- Pasi