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

[Anthony Liguori]

On 11/12/2011 08:43 AM, Avi Kivity wrote:
> On 11/12/2011 03:39 PM, Anthony Liguori wrote:
>> On 11/12/2011 04:27 AM, Avi Kivity wrote:
>>> On 11/11/2011 04:03 PM, Anthony Liguori wrote:
>>>>
>>>> I don't view not supporting migration with image formats as a
>>>> regression as it's never been a feature we've supported.  While there
>>>> might be confusion about support around NFS, I think it's always been
>>>> clear that image formats cannot be used.
>>>
>>> Was there ever a statement to that effect?  It was never clear to me and
>>> I doubt it was clear to anyone.
>>
>> You literally reviewed a patch who's subject was "block: allow
>> migration to work with image files"[1] that explained in gory detail
>> what the problem was.
>>
>> [1] http://mid.gmane.org/4C8CAD7C.5020102@redhat.com
>>
>
> Isn't a patch fixing a problem with migrating image files a statement
> that we do support migrating image files?
>

You know, we could go 9 rounds about this and it really doesn't matter.

For 1.0, I feel very strongly that we cannot change the semantics of migration 
with raw as dramatically as has been proposed.  That's a huge regression risk.

But since live migration with qcow2 has never worked, there's really not a lot 
of harm of adding something that makes qcow2 with live migration work better 
than it does right now.

I just sent out a series that does this.  It's Kevin's original idea since 
actually reopening the file doesn't help anything.  The only thing that's 
different from what I expect Kevin would want is that this is restricted to qcow2.

I want this restrict for 1.0.  If once 1.1 opens up, Kevin wants to promote that 
code to generic block layer code, that's fine with me.

It's also included as part of the migration blockers series so that we are very 
explicit about when we don't support migration for given image formats.

Regards,

Anthony Liguori