(possibly stupid) dedupe question

Aitor_Ibarra · Fri Aug 12, 2011 4:36 pm

Another thread here about DPM/VSS support - http://www.starwindsoftware.com/forums/ ... t2313.html made me think of a client I have and their backups...

Current situation: they run a hyper-v server, with a couple of Windows VMs (including SBS with Exchange). The whole server is backed up every 30mins to external drives using Windows Server Backup, which does a VSS based image backup. Most backups end up being incremental, i.e. really fast, and restore is quick too. This means that when they go home with a disk, they always have an up to date backup, and it works well, except... occasionally WSB runs out of space, so has to wipe some incrementals and do a full backup, which takes longer, and also sometimes they forget to take the disk home.

Now that faster Internet connections are available, direct offsite backup is possible with no disk swapping. E.g. they can get BT Infinity, and that can do about 10Mbit/sec upload, which is enough for incrementals, but not really fast enough for full backups.

Ideally I'd like this client to move to my cloud, but that might not be practical because they really need LAN speed access to the servers. So, next best thing would be:

1) They install Starwind Free on their hyper-v server
2) Instead of backing up to USB drive, they backup to deduped iscsi target
3) the target's image files are actually stored on my Starwind Enterprise HA setup, accessed via a VPN

I think this could work, because even though we wouldn't be able to avoid full backups, they should be quite quick because Starwind's dedupe will spot that the "new" data is mostly duplicated blocks of existing data. This would mean that after the first backup, all backups should be pretty fast.

It hinges on what happens to de-duped targets when data is deleted from them. Is the data really deleted, and therefore de-dupe won't help, or is it left on the disk, deleted as far as the client is concerned, but still there as far as the de-dupe engine is concerned?

Any ideas?

Thanks,

Aitor

Fri Aug 12, 2011 10:32 pm

Aitor sometimes I think you can see future. This time you definitely did. Version of 5.8 of StarWind is going to have Alpha stage of Hyper-V backup. In exactly the way you see - with global deduplication and auxiliary WAN replication (deduplication + compression based).

P.S. Back to dedupe delete. It depends. For now we don't enable real delete so data is stored forever. Like Plan9 FS does (VENTI?). We do have full delete feature but it slows the whole thing to unacceptable performance.