On 28.11.2012 14:00, Jiri Denemark wrote:
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
Oh, right. Then we can't rely on disk ordering neither (well, for now we can because of our code being dumb-enough; but if we change it ...). I should have used device-id instead as it is the only thing that will not change. However, if it ever will - we are gonna need a mapping anyway, so we can map these device-ids then. So the migration cookie should look like this: <nbd> <disk id="drive-virtio-disk0" size="123456"/> ... </nbd> Although, I am not sure whether to include the QEMU_DRIVE_HOST_PREFIX (="drive-") or not. Michal