backing up substantial VM's without centralised data storage (XenServer)

[amfony]

Hi Gang,

 

Another day another question.

 

We run a Xenserver with a handful of utility type service VM's running, it was only ever a P.O.C and nothing of consequence runs on it at this stage. I backup the VM's to a physical file server via XenCentre which depending on the size of the VM can take 10 minutes to 30 mintues. My VM's are currently between 10GB and 30GB usually.

 

I understand that in a mature solution the OS's and DB's would be virtualised and the raw data (CIFS, SMB) would be available and centrealised on a SAN/NAS, this is not that case.

 

If the size of the VM increases significantly, IE 100GB how are backups addressed? As far as i know (limited):

 

Snapshots are not 100%

100% guarenteed backups are achieved only when VM is unavailable

VM size == size of data (no or limited compression)

 

If these are wrong please let me know!

 

So what i do see is this, you can only guarentee backup consistency via taking the VM down, if that VM is significant is size it will just take that long to backup it up to another location.

 

Now i write this it all sounds so obvious but just looking for some concrete answers. Also does anyone know of any good XenServer literature, best practices etc. I know Citrix provide some good docs but i just hate their site lol.

 

Thanks squadron

[dhicks]

I understand that in a mature solution the OS's and DB's would be virtualised and the raw data (CIFS, SMB) would be available and centrealised on a SAN/NAS, this is not that case.

 

You don't nccesarily need a central store for virtual machines, mirroring of volumes between servers can work equally well.

 

So what i do see is this, you can only guarentee backup consistency via taking the VM down, if that VM is significant is size it will just take that long to backup it up to another location.

 

Backup time shouldn't affect the time you can bring your VM back up in - take the VM down, snapshot the sotrage volume, bring the VM back up and backup the snapshotted volume. When done, you should be able to remove the snapshot without having to take the VM down again. Downtime should be a couple minutes at the most.

 

--

David Hicks

[morganw]

You could use the free version of Alike to backup one physical Xenserver machine to one physical backup machine, if you register you can do multiple physical Xenserver machines to a single backup machine. The backup is based on a snapshot so there isn't any down time and has block level de-duplication to only store changes. When combined with a file system level backup just for home folders and shared storage this should cover everything from massive failure of a Xenserver host through to Joe User deleting something he shouldn't have and wanting it restored.