I would suspect that quite a lot fall into 1 On 3 May 2016 at 16:33, David Medberry <openst...@medberry.net> wrote:
> The only reason I can think of is that they are doing nested VMs and don't > have the right nesting flag enabled in their base flag. > > On Tue, May 3, 2016 at 9:01 AM, Daniel P. Berrange <berra...@redhat.com> > wrote: > >> Hello Operators, >> >> One of the things that constantly puzzles me when reading the user >> survey results wrt hypervisor is the high number of respondants >> claiming to be using QEMU (as distinct from KVM). >> >> As a reminder, in Nova saying virt_type=qemu causes Nova to use >> plain QEMU with pure CPU emulation which is many many times slower >> to than native CPU performance, while virt_type=kvm causes Nova to >> use QEMU with KVM hardware CPU acceleration which is close to native >> performance. >> >> IOW, virt_type=qemu is not something you'd ever really want to use >> unless you had no other options due to the terrible performance it >> would show. The only reasons to use QEMU are if you need non-native >> architecture support (ie running arm/ppc on x86_64 host), or if you >> can't do KVM due to hardware restrictions (ie ancient hardware, or >> running compute hosts inside virtual machines) >> >> Despite this, in the 2016 survey 10% claimed to be using QEMU in >> production & 3% in PoC and dev, in 2014 it was even higher at 15% >> in prod & 12% in PoC and 28% in dev. >> >> Personally my gut feeling says that QEMU usage ought to be in very >> low single figures, so I'm curious as to the apparent anomoly. >> >> I can think of a few reasons >> >> 1. Respondants are confused as to the difference between QEMU >> and KVM, so are saying QEMU, despite fact they are using KVM. >> >> 2. Respondants are confused as to the difference between QEMU >> and KVM, so have mistakenly configured their nova hosts to >> use QEMU instead of KVM and suffering poor performance without >> realizing their mistake. >> >> 3. There are more people than I expect who are running their >> cloud compute hosts inside virtual machines, and thus are >> unable to use KVM. >> >> 4. There are more people than I expect who are providing cloud >> hosting for non-native architectures. eg ability to run an >> arm7/ppc guest image on an x86_64 host and so genuinely must >> use QEMU >> >> If items 1 / 2 are the cause, then by implication the user survey >> is likely under-reporting the (already huge) scale of the KVM usage. >> >> I can see 3. being a likely explanation for high usage of QEMU in a >> dev or PoC scenario, but it feels unlikely for a production deployment. >> >> While 4 is technically possible, Nova doesn't really do a very good >> job at mixed guest arch hosting - I'm pretty sure there are broken >> pieces waiting to bite people who try it. >> >> Does anyone have any thoughts on this topic ? >> >> Indeed, is there anyone here who genuinely use virt_type=qemu in a >> production deployment of OpenStack who might have other reasons that >> I've missed ? >> >> Regards, >> Daniel >> -- >> |: http://berrange.com -o- >> http://www.flickr.com/photos/dberrange/ :| >> |: http://libvirt.org -o- >> http://virt-manager.org :| >> |: http://autobuild.org -o- >> http://search.cpan.org/~danberr/ :| >> |: http://entangle-photo.org -o- >> http://live.gnome.org/gtk-vnc :| >> >> _______________________________________________ >> OpenStack-operators mailing list >> OpenStack-operators@lists.openstack.org >> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators >> > > > _______________________________________________ > OpenStack-operators mailing list > OpenStack-operators@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-operators > > -- DataCentred Limited registered in England and Wales no. 05611763
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