What about RSync, can it be used to suit your needs and requirements ?
Just curious, what O/S are you offering to your customers for those VPS (Linux or Windows), and what is that "complete office data" you're talking about? I thought you wanted to offer them a complete backup system for their websites/emails?
All data is stored on a RAID10 SAN, and if you have backups enabled for your system these will be stored away from the primary data store.
Once backups are enabled on your system, it will automatically be backed up every day, and archived every week and every month, so you will always have the opportunity to roll back your VPS in case something goes wrong.