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Re: [libvirt] [PATCH v1 00/11] Rework storage migration



On Wed, Nov 28, 2012 at 10:31:54 +0800, li guang wrote:
> 在 2012-11-27二的 16:42 -0500,Eric Blake写道:
> > > This patch set re-implements migration with storage for enough new
> > > qemu.
> > 
> > How does this series interact with Li Guang's efforts to add offline
> > migration?  In particular,
> > 
> > > 1)  src -> dest: (QEMU_MIGRATION_PHASE_BEGIN3 ->
> > > QEMU_MIGRATION_PHASE_PREPARE)
> > >     <nbd>
> > >        <disk src='/var/lib/libvirt/images/f17.img'
> > >        size='17179869184'/>
> > >     </nbd>
> > 
> > Both sets of patches need to pass size information across in the
> > cookies; so is tying it to <nbd> appropriate, or should we be
> > rethinking this XML to be shared between both patches?
> 
> actually, I think 'src' is unnecessary, for 'def->disks[i]->src'

'src' is not only unnecessary it's actually totally useless since we can't
rely on it. In case a domain is migrated to a host with pre-migration hook
installed, the hook is allowed to modify parts of the XML that are not visible
to the domain. And disk source is one of them. (The same applies for
specifying the XML to be used on destination directly to virDomainMigrate*
APIs.) In other words, disk source on destination does not have to match the
path on source host.

Jirka


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