I just put my new all-in-one fileserver [called 'sunbeam'] into production. It's a Athlon64 based system, with five 200GB SATA drives. Since there's now a working (but still unofficial) Debian AMD64 Port, I can even run a 64bit distribution on it. As far as production machines go, I have the policy to only run debian on them.
This machine replaces the old box [now called 'shiva'], (Athlon 1000 with eight hard drives 80-120GB] which now serves as main storage server for my network-wide backup system.
As new backup solution, I chose to use Bacula. The architecture just looks like the 'right thing'. The catalog is maintained in the SQL RDBMS of your choice, every to-be-baked-up machine runs a client (bacula-fd). A director running on one server then directs the clients to write their data to one or more storage servers of their choice. This now also means that I can have one centralized directore for three different physical locations (yes, my machines are spread over three distinct locations with low bandwidth interconnection). Every location just has it's own storage server :). Oh yes, of course, this is on-site backup to hard drives only. Won't help if my house went fire.