Build a cheap terabyte Linux file server

We wanted a large >= 1TB file server mostly to store backups.

Well I looked at some commercial options and most of them came in at about $20000, and lacked the ability to be easily expanded. The only option to expand a lot of the commercial options was to add another unit and split your data across two of them. It was the lack of easy expandability that actually won the day. A lot of the commercial options are very similar to what I build, a lot of them even use the 3ware cards which I was considering.