I've been using OMV for some time and as I start playing with different plugins as well as installing debian packages and some minor hacks of my own, I am getting a bit anxious that something could go wrong... For this reason I would like to share some thoughts on the backup topic and hopefully receive some ideas how to find a satisfying backup solution for my OMV system.
I have found out that making differential backups with rsync is quite easy, and in my opinion also elegant. Elaborating a little bit with the code in 'mikes handy rotating-filesystem-snapshot utility' (reference below) I have put together a small script which is called from cron to make snapshots once a day. (I'll be happy to share it if anyone is interested, I was surprised to find that a snapshot backup only takes a few seconds and that it uses less space on the disk than I had expected.)
Part two of the problem = to recover from an existing backup, does however seem to be a harder nut to crack for me. My idea was to use two separate system partitions for my OMV system (my 32 GB ssd drive is big enough to do so). Using gparted I have therefore resized and split the OMV system partition in two 8 GB partitions (I call them OMV_OS1 & OMV_OS2) and also formatted the new (empty) partition as ext4.
I have put together a recovery script that copies the contents from the backup onto the 8 GB which is currently not in use. The idea was that the same script should then swap the UUID's of OMV_OS1/2 and then reboot. My idea was that this way grub, fstab and OMV would not be affected of the change, so that OMV would just boot into the recovered system and behave as if nothing had happened.
Initially the approach was promising but after some testing I am not sure it is such a good idea anymore. It seems that a command like df is now listing both partitions as /dev/sdb3, when one is actually /dev/sdb1...
Any ideas what is going on? Are there any better solutions for recovery? Perhaps one where you would not even need a spare partition?
Below are three links which I found interesting, maybe you do as well 
gpetrom's thread about backup with rsync : http://forums.openmediavault.o…4&p=525&hilit=backup#p525
ppfdez's thread about howto use gparted on your OMV drive: http://forums.openmediavault.o…&p=734&hilit=gparted#p734
mikes handy rotating-filesystem-snapshot utility: url]http://www.mikerubel.org/computers/rsync_snapshots/[/url]