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

["Tiziano Müller" <tiziano.mueller@stepping-stone.ch>]

Am Montag, den 15.10.2012, 09:48 +0200 schrieb Stefan Hajnoczi:
> Okay, that's consistent with the other symptoms you've reported.
> 
> It's not clear whether the corruption arises inside qcow2 or if
> something else is causing corruption and qcow2/xfs get upset.  That is
> the next step to debugging this - hopefully it will become possible to
> reproduce it reliably, at which point it is much easier to debug :).

Yes, we have now 3 different VM-configurations deployed on the server
where we saw the most corruptions so far:

* config 1: as-is
* config 2: raw-image format instead of qcow2 as you suggested
* config 3: vhost=off for the network

The third test-case is because we figured out that one major difference
between the two servers is that on the server with the most corruptions
we have vhost=on (automatically turned on by qemu/libvirt because the
vhost-net module got loaded). I know this does not make a lot of sense.

In fact, on the server without vhost-net (and with qemu-1.0) we only saw
one corruption after all (where the qcow2 got really messed up), so one
could assume that this was a single event and may have been a user
error. To summarize it:

* server 1 (qemu-kvm-1.1, host-kernel 3.5.2, vhost-net loaded and used)
has had +5 machines with corrupt filesystems (ext4 and xfs) and 1
machine with a corrupt qcow2.
* server 2 (qemu-kvm-1.0, host-kernel 3.2.6, vhost-net not loaded) has
had only 1 machine with a corrupt qcow2.

The mentioned Test-VMs are running since Friday and unfortunately none
of them had the decency to go corrupt again.

We will keep you posted,
thanks a lot for your help.

Best regards,
Tiziano

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