[CentOS-virt] moving from Xen to KVM
pasik at iki.fi
Thu Mar 18 20:34:31 UTC 2010
On Wed, Mar 17, 2010 at 03:49:40PM -0700, Grant McWilliams wrote:
> On Wed, Mar 17, 2010 at 6:35 AM, Dennis J. <dennisml at conversis.de>
> On 03/17/2010 02:15 PM, Hildebrand, Nils, 232 wrote:
> > Hi,
> > I have 31 DomUs up and running on a single Box - and have a strong
> feeling that even 60 will run flawless.
> > But: All of them are Para-Virtualized.
> > I have no problem with disk IO-Bottlenecks since my DomUs are not
> Database-Servers - so there is mostly static information in the
> The term "paravirtualization" is becoming quite dated. Even if you
> a KVM guest without that option if you choose the virtio driver inside
> you still end up with "paravirtualized" I/O. With the advent of things
> nested page tables and SR-IOV the "fully virtualized=slow,
> paravirtualized=way faster" logic is no longer necessarily true at least
> not for every aspect of the system.
> Â Dennis
> In the Xen world paravirtualizing will be replaced by Hybrid virtualizing.
> As hardware virt becomes faster (ie, not so slow) then Xen will change to
> using HVM as the default and paravirtualize EVERYTHING else. This is not
> the same thing as KVM which uses hardware virt for cpu, emulation for most
> things except disk and network which are paravirtualized (if chosen). I
> look forward to this as HVM in Xen is slower than KVM even though it's
> kind of doing the same thing.Â However, I don't think people have
> benchmarked either enough to realize how much of a hit we're taking with
Do you have some benchmarks showing Xen HVM is slower than KVM?
I believe so far Xen HVM has actually been faster than KVM.
> KVM has some neat tricks up their sleeve as well like shared memory,
> nesting etc.. I may put up a KVM box just because I need nesting (for a
> classroom to teach virtualization).
Lately Xen has gotten a couple of different types of memory sharing implementations aswell.
At least one of them will ship in upcoming Xen 4.0.0.
> Grant McWilliams
> Some people, when confronted with a problem, think "I know, I'll use
> Now they have two problems.
> Visible links
> 1. mailto:dennisml at conversis.de
> CentOS-virt mailing list
> CentOS-virt at centos.org
More information about the CentOS-virt