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Date: Mon, 10 Dec 2007 11:45:39 +0100
From: Lorenzo Mancini <lmancini@develer.com>
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Subject: Re: [Qemu-devel] Online image backup
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To: qemu-devel@nongnu.org

Ricardo Almeida wrote:

>> Fabrice, that's just part of the problem.  A full automated remote
>> backup service for qemu VMs should work like this:
>>
>>   1. send a "savevm state" command to qemu;
>>   2. wait for savevm completion;
> 
> 2.1 Switch to snapshot mode

How do you switch to snapshot mode *while* the VM is running, i.e. 
without stopping and restarting qemu?  The only way I know to enter that 
mode is using the -snapshot switch at invocation time and I don't think 
it can be done online.


>>   3. perform an *online* copy (cp, rsync, whatever) of the .qcow2 image,
>> while it's still running in qemu;
> 
> 3.1 Pause VM
> 3.2 Apply snapshot changes to local and remote copy (remote must be
> running something that can apply the update)
> 3.3 Back to normal mode

If executing step 2.1 is actually possible, you can skip step 3.1 and 
3.2 because the remote copy is already consistent with the state the VM 
went throught at the time of execution of step 2.1 .  If it was 
possible, it would be just fine for automated daily backups.

-- 
Lorenzo Mancini