ZFS might be what you need (Score 1)

I recommend using ZFS on OpenSolaris. Create one massive storage pool from multiple drives, and then create as many file systems as you require. Each file system consumes as much of the storage pool as it needs, and if required, a file system's space can be constrained or guaranteed using quotas and reservations. Thus, no shrinking is required. Also, Solaris has Zones you can run other OSes in too. See here: http://breden.org.uk/2008/03/02/a-home-fileserver-using-zfs/