From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: [Qemu-devel] Re: KVM call minutes for June 8
Date: Thu, 10 Jun 2010 09:27:34 -0500
Message-ID: <4C10F656.20305@codemonkey.ws>
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Cc: "Daniel P. Berrange" <berrange@redhat.com>,
	Chris Wright <chrisw@redhat.com>,
	kvm-devel <kvm@vger.kernel.org>, armbru@redhat.com,
	qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
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On 06/10/2010 08:08 AM, Kevin Wolf wrote:
> Am 10.06.2010 14:53, schrieb Anthony Liguori:
>    
>> On 06/10/2010 04:43 AM, Kevin Wolf wrote:
>>      
>>> Huh, why this? Seems I still haven't understood all of qcow2 then... I
>>> always thought that there's just a specific offset where VM state
>>> starts, but no explicit end.
>>>
>>>        
>> A live snapshot can last for a very long time.  What happens if you need
>> to allocate a new block for disk I/O while saving a snapshot?
>>      
> You allocate it, I guess?
>
> Note that VM state must be virtually contiguous, but not necessarily
> physically (virtually = on the virtual hard disk as seen by the guest;
> physically = in the image file). It's just not seen by the guest because
> it's saved at a high offset that is after the end of the real disk
> content, but otherwise it should behave the same as guest data.
>    

I guess you could just start writing and then once your finished, you 
could update the snapshot information.  So yeah, I think your right that 
it's doable with the current format.

Regards,

Anthony Liguori

> Kevin
>