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? Lorin
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