Just wondering how big your backup store grows in comparison to the amount of data to be backed up?

I'm just trying to plan out how much space we'll need to get for our new backup server, which will probably be a basic server with some 2TB SATA disks.

We'll also have our current DL380 G4 storage server with 6 x 300GB SCSI disks going spare so might be able to use that, with RAID5 that would give 1.2TB if we keep a hot spare.

We're currently backing up around 500GB of data but I expect that to go up a bit in order to back up the VMs as well...