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Date: Thu, 10 Mar 2011 10:59:04 +0100
From: Jes Sorensen <Jes.Sorensen@redhat.com>
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Subject: Re: [Qemu-devel] Issue with snapshot outside qcow2 disk - qemu 0.14.0
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: SAURAV LAHIRI <saurav_lahiri@yahoo.com>, qemu-devel@nongnu.org

On 03/10/11 10:58, Stefan Hajnoczi wrote:
> On Thu, Mar 10, 2011 at 9:32 AM, Jes Sorensen <Jes.Sorensen@redhat.com> wrote:
>> On 03/10/11 10:27, Stefan Hajnoczi wrote:
>>> I have CCed Jes who has been working on a live snapshot mechanism.  He
>>> recently added the snapshot_blkdev monitor command that takes a
>>> snapshot of a block device while the VM is running.  A new image file
>>> is created based off the original image file (which will no longer be
>>> modified), all new disk writes go to the new image file.  It is safe
>>> to perform read-only access to the original image file.  There
>>> currently is no support to merge the snapshot changes back into the
>>> original image while the VM is running, but I think that is the next
>>> planned step.
>>
>> Yes, keep in mind that the live snapshot is only for external snapshot
>> files, it doesn't deal with internal snapshots.
> 
> Yep, that's why I'm interested in Saurav's use case.  Many use cases
> work with either internal or external snapshot but it depends on the
> details.

Actually I think there's very little reason to keep internal snapshot
support. It doesn't buy us much, but it adds unnecessary complexity.

Cheers,
Jes