> I would use ffs without softdep, since you have hardware raid.

Why?  Softdep and raid solve different problems.

I've been using softdep with SATA on FreeBSD 6.0 for about a
year and it works great.  Background fsck "just works" out of
the box.

Yes, there is a lot of disk i/o during background fsck,
but the system is up and usable.  The only thing fsck is
doing is looking for lost blocks, so you could suspend it
if you need the system to be at full speed.

>> (I can't really imagine backing a 500 GB file system to
>> a tape drive.  There are tape drives that can hold hundreds
>> of GBs, but i can't afford them. :)

Yeah, backups are a problem.  Choices include a very expensive
tape drive, additional hard drives (and perhaps controllers),
a DVD writer and a very large number of blank DVDs.  Hopefully
the prices of Blu-Ray and HD-DVD drives and blank media will
come down, but that doesn't help today.