On Wed, Mar 17, 2010 at 03:49:40PM -0700, Grant McWilliams wrote:
On Wed, Mar 17, 2010 at 6:35 AM, Dennis J. <[1]dennisml@conversis.de> wrote:
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 filesystems. The term "paravirtualization" is becoming quite dated. Even if you install a KVM guest without that option if you choose the virtio driver inside then you still end up with "paravirtualized" I/O. With the advent of things like 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. Regards,  DennisIn 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. However, I don't think people have benchmarked either enough to realize how much of a hit we're taking with virtio.
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.
-- Pasi
Grant McWilliams
Some people, when confronted with a problem, think "I know, I'll use Windows." Now they have two problems.
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