Re: [BackupPC-users] Backup of virtual machines

Le 04/07/2016 à 14:01, Smith, Graham - Computing Technical Officer a écrit :

I don't use xenserver but my generic advice as a strategy would be to backup the contents of the VMs rather than the raw virtual disks.

Effetively treating the guests as if they were physical systems. The raw virtual disk files will be large but also non-unique so will cost a lot more

in storage space in your backups and potentially take a lot more time to backup. Backing up the files contained within the VMs should save space

with BackupPC in taking full advantage of single instance storage of repeated files in your pool common to many users or host systems.

You can have both: save full image while storing only the delta between two backups.

Here's what I've written: http://gitweb.firewall-services.com/?p=virt-backup;a=blob_plain;f=virt-backup;hb=HEAD

I use it only on KVM, but should work with anything libvirt supports. I use it in combination with BackupPC (as pre dump and post dump script)

The basic idea is:

- Suspend the VM
- take a snapshot of the underlying storage (using LVM)
- Resume the VM (so it has only been suspended for a very short time, usually not even noticeable)
- Using chunkfs, mount the image (file or raw block) as a set of chunks of fixed size: there's no copy, the fuse mount point is virtual, and ready from it will read in fact from the snapshot, except that it'll be pesented as a set of small chunks
- Using BackupPC, backup all those chunks
- When done, unmount the fuse file system and remove the snapshot

Now, the next backup will only store chunks which have changed, which is usually not a lot

++

Logo FWS

Daniel Berteaud

FIREWALL-SERVICES SAS.
Société de Services en Logiciels Libres
Tel : 05 56 64 15 32
Visio : http://vroom.im/dani
www.firewall-services.com

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