On Wednesday 05 March 2014 16:59:24 Andreas Färber wrote: > Am 30.01.2014 19:23, schrieb Neil Skrypuch: > > First, let me briefly outline the way we use live migration, as it is > > probably not typical. We use live migration (with block migration) to > > make backups of VMs with zero downtime. The basic process goes like this: > > > > 1) migrate src VM -> dest VM > > 2) migration completes > > 3) cont src VM > > 4) gracefully shut down dest VM > > 5) dest VM's disk image is now a valid backup > > > > In general, this works very well. > > > > Up until now we have been using qemu-kvm 1.1.2 and have not had any issues > > with the above process. I am now attempting to upgrade us to a newer > > version of qemu, but all newer versions I've tried occasionally result in > > the virtio- net device ceasing to function on the src VM after step 3. > > While I don't know this particular symptom, I can definitely tell you > that migrating from qemu-kvm to qemu is bound to fail unless you enable > at least a version_id change in piix4.c, possibly also in kvmvapic.c. > Such errors would lead to migration not successfully completing though, > with cryptic error on the dest side. > > Regards, > Andreas
I should clarify, all of these migrations happen from same version to same version (and same host to same host). So 1.7.0 -> 1.7.0, 1.6.0 -> 1.6.0, etc. What we're looking for out of this is a clean copy of the disk image (consistent and from a graceful shutdown) for backup purposes, without having to shut down the VM. I expected cross-version migration to be dicey and made a point of avoiding it. - Neil
