Re: qemu and qemu.git -> Migration + disk stress introduces qcow2 corruptions

[Juan Quintela <quintela@redhat.com>]

"Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Wed, Nov 09, 2011 at 11:35:54AM -0600, 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.
>
> A simple solution is not to do any probing before the VM is first
> started on the incoming path.
>
> Any issues with this?

hw/pc.c:cmos init of the devices needs to know the geometry.

But looking at the code, "perhaps" this commit has made things work
correctly even if we open them late.  Something like this was the idea
that Anthony suggested last time I showed the problem.

Later, Juan.

commit c0897e0cb94e83ec1098867b81870e4f51f225b9
Author: Markus Armbruster <armbru@redhat.com>
Date:   Thu Jun 24 19:58:20 2010 +0200

    pc: Fix CMOS info for drives defined with -device