I think that one way to do this is to set up a drive volume solely for backups. So let’s say you have 5 users and want to guarantee each of them 20mb for backup.

Buy a 120gb drive (internal or external), hang it off your server. (You’ll need more than a 100gb drive because you don’t get a full 100gb from a 100gb drive.) Or take an existing drive and repartition it to provide a new 100gb partition.

Then you can create /Volumes/backups/user1, /Volumes/backups/user2, etc on that drive, enable a 20gb quota for each, and get the effect you want.

If you’re not running a large rack mounted RAID configuration already, consider buying one of the RAID external drive cases, such as that provided by OWC or the “Venus” model from AMS (you can Google ‘venus RAID’ to get multiple sources.)

Another really cheap option right now is that several drive makers have USB 2.0/FW400 external drives on sale cheap. Since you’re talking about this for backup, dri8ve performance isn’t an issue. (The OWC and Venus RAID cases are both FW -800-, and FW800 performance is quite nice!).

Don’t forget though, that a backup strategy that doesn’t provide for off-site storage is really not complete. (I’m guilty of this, my plan is to use two of my external drives as an offsite backup for important data, stored at a friend’s house. Every so often I’ll swap the external drives with him.)

Separate topic: I’m on the hook to write an article on ‘at-home use of OS X server’. If you’re using X Server for home/home office/really small business, I’d like to hear from you. ([email protected])

dave