Re: [Qemu-devel] qemu and qemu.git -> Migration + disk stress introduces qcow2 corruptions

[Avi Kivity <avi@redhat.com>]

On 11/09/2011 07:35 PM, Anthony Liguori wrote:
> On 11/09/2011 11:02 AM, Avi Kivity wrote:
>> On 11/09/2011 06:39 PM, Anthony Liguori wrote:
>>>
>>> Migration with qcow2 is not a supported feature for 1.0.  Migration is
>>> only supported with raw images using coherent shared storage[1].
>>>
>>> [1] NFS is only coherent with close-to-open which right now is not
>>> good enough for migration.
>>
>> Say what?
>
> Due to block format probing, we read at least the first sector of the
> disk during start up.
>
> Strictly going by what NFS guarantees, since we don't open on the
> destination *after* as close on the source, we aren't guaranteed to
> see what's written by the source.
>
> In practice, because of block format probing, unless we're using
> cache=none, the first sector can be out of sync with the source on the
> destination.  If you use cache=none on a Linux client with at least a
> Linux NFS server, you should be relatively safe.
>

IMO, this should be a release blocker.  qemu 1.0 only supporting
migration on enterprise storage?

If we have to delay the release for a month to get it right, we should. 
Not that I think we have to.

-- 
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