Once again, I urge anyone who needs anything like this to consider Olivier Cochard-Labbe's "FreeNAS" -
FreeNAS: The Free NAS Server - Home
This is a fully-fledged NAS application running under BSD Unix and getting better all the time. The versatility and flexibility of this NAS server is phenomenal.
I use it for office backup. Booting from a USB stick and using rsync the NAS runs a silent incremental daily backup of each of 8 people in the office, each to their own directory, accessible only to them on HDD1. It does a weekly rsync to HDD2 and a monthly rsync to HDD3.
Administration is through a very well crafted Web interface.
Makes yer average NAS box look like a kids toy.
Mac