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Re: [Qemu-devel] Re: KVM call minutes for June 8


From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: KVM call minutes for June 8
Date: Thu, 10 Jun 2010 09:27:34 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100423 Lightning/1.0b1 Thunderbird/3.0.4

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




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