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 at 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, >  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. 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. > > References > > Visible links > 1. mailto:dennisml at conversis.de > _______________________________________________ > CentOS-virt mailing list > CentOS-virt at centos.org > http://lists.centos.org/mailman/listinfo/centos-virt