RAID5 for Linux

[bob at sinister.com (Bob Keyes)]

At my new job, we have a NAS "Snap Appliance", which is pretty horrible
and I want to get rid of it. So I am going to push for a Linux solution.
I'd want RAID level 5, and Serial ATA drives, and of course linux
niceness. I was looking at the Adaptec 2810SA, but it's got 8 ports..I
though you needed 9 for RAID5 (one for each bit plus one parity) or am I
misunderstanding this? I'd also want hot-swappable. Anyone have any
suggestions?

For backup, I am thinking the Sony AIT-2 changer, LIB-D81/A2. Don't know
if it's compatible with Bacula though...