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Date: Thu, 10 Jun 2010 15:08:02 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] Re: KVM call minutes for June 8
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Chris Wright <chrisw@redhat.com>, kvm-devel <kvm@vger.kernel.org>, qemu-devel@nongnu.org, armbru@redhat.com, Luiz Capitulino <lcapitulino@redhat.com>

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.

Kevin