Re: [Qemu-devel] Silent filesystem/qcow2 corruptions with qemu-kvm-1.0 and 1.1.1

[Kevin Wolf]

Am 12.10.2012 10:53, schrieb Tiziano Müller:
> Am Freitag, den 12.10.2012, 10:33 +0200 schrieb Stefan Hajnoczi:
>> On Thu, Oct 11, 2012 at 03:33:23PM +0200, Tiziano Müller wrote:
>>> Checking the image using `qemu-img check` then gives something like
>>> this:
>>>
>>> ERROR OFLAG_COPIED: offset=3bc30000 refcount=1
>>> ERROR offset=c7e331: Cluster is not properly aligned; L2 entry
>>> corrupted.
>>
>> Is any other program accessing the qcow2 image on the host while the VM
>> is running?
> 
>> For example, are you running qemu-img on the image while the VM is
>> running?
> 
> On some VMs we tried to extract filesystem snapshots at runtime:
> 
>   qemu-img convert -s snapshot-id original.qcow2 snapshot.qcow2
> 
> (yes, that's not consistent, we're switching to external snapshots).
> But that should open the image read-only, right?

Yes, in theory that should be harmless and even produce a correct copy
of the snapshot.

> Other operations where the qemu-monitor-commands "savevm" and "delvm". 
> 
> Although: we created a new qcow2 and even in that the filesystem got
> corrupted without any of the above actions. So we're pretty confident
> that those operations are not the sole cause.

So no internal snapshots are involved at all with this new image? I'm
asking because in the past non-reproducible failures were reported with
snapshots, but I'm not aware of any case that didn't use snapshots.

Any other non-default feature that you used, like compression?

Kevin