On Wed, Apr 24, 2013 at 05:23:11PM -0400, Lorin Hochstein wrote: > On Wed, Apr 24, 2013 at 11:59 AM, Daniel P. Berrange <d...@berrange.com>wrote: > > > On Wed, Apr 24, 2013 at 11:48:35AM -0400, Lorin Hochstein wrote: > > > In the docs, we describe how to configure KVM block-based live migration, > > > and it has the advantage of avoiding the need for shared storage of > > > instances. > > > > > > However, there's this email from Daniel Berrangé from back in Aug 2012: > > > http://osdir.com/ml/openstack-cloud-computing/2012-08/msg00293.html > > > > > > "Block migration is a part of the KVM that none of the upstream > > developers > > > really like, is not entirely reliable, and most distros typically do not > > > want to support it due to its poor design (eg not supported in RHEL). > > > > > > It is quite likely that it will be removed in favour of an alternative > > > implementation. What that alternative impl will be, and when I will > > > arrive, I can't say right now." > > > > > > Based on this info, the OpenStack Ops guide currently recommends against > > > using block-based live migration, but the Compute Admin guide has no > > > warnings about this. > > > > > > I wanted to sanity-check against the mailing list to verify that this was > > > still the case. What's the state of block-based live migration with KVM? > > > Should we say be dissuading people from using it, or is it reasonable for > > > people to use it? > > > > What I wrote above about the existing impl is still accurate. The new > > block migration code is now merged into libvirt and makes use of an > > NBD server built-in to the QMEU process todo block migration. API > > wise it should actually work in the same way as the existing deprecated > > block migration code. So if you have new enough libvirt and new enough > > KVM, it probably ought to 'just work' with openstack without needing > > any code changes in nova. I have not actually tested this myself > > though. > > > > So we can probably update the docs - but we'd want to checkout just > > what precise versions of libvirt + qemu are needed, and have someone > > check that it does in fact work. > > > > > Thanks, Daniel. I can update the docs accordingly. How can I find out what > are the minimum versions of libvirt and qemu are needed? > > Also, I noticed you said "qemu" and not "kvm", and I see that > http://wiki.qemu.org/KVM says that qemu-kvm fork for x86 is "deprecated, > use upstream QEMU now". Is it the case now that when using KVM as the > hypervisor for a host, an admin will just install a "qemu" package instead > of a "qemu-kvm" package to get the userspace stuff?
It depends on the distro to be honest. eg on Fedora you'd use qemu-kvm which is a virtual package which will pull in qemu-system-$ARCH for your particular host. 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 :| _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : openstack@lists.launchpad.net Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
