Re: [Qemu-devel] [PATCH 3/4] Purge migration of (almost) everything to do with monitors

[Eric Blake <eblake@redhat.com>]

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On 03/09/2012 11:53 AM, Anthony Liguori wrote:
>>>
>>> Could we just remove block migration entirely...
>>
>> Libvirt has already exposed block migration to users,
> 
> :-(
> 
> Do you rely on the progress stats that are printed?

I've never personally used it (as I said earlier, the libvirt support
for blk and inc doesn't get much testing), but I can state that if you do:

virsh migrate --copy-storage-all --copy-storage-inc --verbose ...

that virsh will cause libvirt to start up a detached migration, then
repeatedly call the query-migrate monitor command to update an on-screen
progress monitor to the user; this progress monitor tracks both ram and
disk status to compute the percentage complete showed to the user, so at
some level, libvirt really is trying to rely on accurate block migration
progress numbers.

>> regularly get people complaining that they don't have shared storage set
>> up, and they are looking for a magic bullet that will do block migration
>> alongside the domain migration; perhaps libvirt can still provide that
>> with block mirroring or other (working) solutions from the same API it
>> gives to the user if you end up pulling it out of the migrate QMP
>> command.
> 
> Well block mirroring is hopefully around the corner.

Just so I'm clear, are you talking about a more complete mirroring
solution than just the storage migration use of mirroring that enables
live block migration without also migrating VM state?  Also, is this a
qemu 1.1 planned feature, or will it more likely be in the 1.2 timeframe?

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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