[sheepdog-users] About snapshots

[Ing. Luca Lazzeroni - Trend Servizi Srl]

Il giorno 16/ago/2013, alle ore 11:03, Liu Yuan <namei.unix at gmail.com> ha scritto:

> On Fri, Aug 16, 2013 at 10:48:17AM +0200, Ing. Luca Lazzeroni - Trend Servizi Srl wrote:
>> Hi,
>> I'm trying to use external snapshot feature of QEMU/libVirt with sheepdog baked vdi to take VDI live backups without using sheepdog snapshots.
>> This is to avoid the problem of disk-space unreleased on snapshot deletion.
> 
> Maybe you can simply use qemu-img sheepdog:image local_iamge to read the image
> out of cluster?
> 

Yes, I could, but I need "live" backups, so I can't stop the running vm and backing up the VDI of a running VM can lead to data corruption,

> The release of unused objects from deleted snapshots will be supported in the
> up comming series of v0.7.x, I guess in about one month or two.
> 

Good, but I'm trying to find out a "tricky" solution in the meantime :-)

>> The main problem is that virsh seems to fail to create external snapshot (baked on qcow2 files on local server filesystem) on vm running within sheepdog, probably due to qemu inability to create disk-mirror across the 2 storage technologies (sheepdog / local fs).
>> 
>> Is anyone trying to do this ? Or is this the wrong way to take full backups ?
> 
> I think 'dog cluster snapshot' will serve you better for 'full backups'
> 

Does this command stop/block VM during the backup ?
If this creates snapshot on cluster, I think it created automatically snapshot of any vdi on it. Are they occupying space on cluster after backup terminated ?

Thank you again,

> See https://github.com/sheepdog/sheepdog/wiki/Backend-Stores%2C-Object-Cache-and-Disk-Cache#cluster-backup
> 
> Thanks
> Yuan

Ing. Luca Lazzeroni - Trend Servizi Srl
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