Re: [Qemu-devel] [question] incremental backup a running vm

[Zhang Haoyu]

On 2015-01-23 07:30:19, Kashyap Chamarthy wrote:
>On Wed, Jan 21, 2015 at 11:39:44AM +0100, Paolo Bonzini wrote:
> > 
> > 
> > On 21/01/2015 11:32, Zhang Haoyu wrote:
> > > Hi,
>> > 
> > > Does drive_mirror support incremental backup a running vm?
> > > Or other mechanism does?
> > > 
>> > incremental backup a running vm requirements:
> > > First time backup, all of the allocated data will be mirrored to 
> > > destination,
> > > then a copied bitmap will be saved to a file, then the bitmap file will 
> > > log dirty for
> > > the changed data.
> > > Next time backup, only the dirty data will be mirrored to destination.
>> > Even the VM shutdown and start after several days,
> > > the bitmap will be loaded while starting vm.
> > > Any ideas?
> > 
>> Drive-mirror is for storage migration.  For backup there is another job,
> > drive-backup.  drive-backup copies a point-in-time snapshot of one or
> > more disks corresponding to when the backup was started.
> 
> Zhang, I've been testing the `drive-backup` command via QMP for a little
>while, and it works reasonably well. If you'd like to test it you can
> quickly try as below, once you have a QEMU instance runing with QMP
> (I invoke my QEMU instances with '-qmp tcp:localhost:4444,server').
> 
Hi, Kashyap
I've tried ‘drive_backup’ via QMP,
but the snapshots were missed to backup to destination,
I think the reason is that backup_run() only copy the
guest data regarding qcow2 image.

Thanks,
Zhang Haoyu
>The below script invokes the 'drive-backup' QMP command (Ensure you're
> using the correct disk, your disk ID might be 'drive-virtio-disk1' :-) )
> -----------------
> #!/bin/bash
> set -x
>exec 3<>/dev/tcp/localhost/4444
> echo -e "{ 'execute': 'qmp_capabilities' }" >&3
> read response <&3
> echo $response
>echo -e "{ 'execute': 'drive-backup', 'arguments':
>       { 'device': 'drive-virtio-disk0', 'sync': 'full', 'target':
>       '/export/backup-of-vm1.qcow2', 'mode': 'absolute-paths', 'format': 
> 'qcow2' } }" >&3
> read response <&3
> echo $response
>-----------------
> 
> Once the above is invoked succesfully, you can see the success of the
> command on the shell where your QMP server is running:
>-----------------
> [. . .]
> char device redirected to /dev/pts/8 (label charserial0)
> QEMU waiting for connection on: disconnected:tcp:localhost:4444,server
> Formatting '/export/backup-of-vm1.qcow2', fmt=qcow2 size=53687091200 
> encryption=off cluster_size=65536 lazy_refcounts=off 
>-----------------
> 
> 
> > Incremental backup is being worked on.  You can see patches on the list.
> 
> 
> -- 
> /kashyap