Digital BW, The Print

Just to add a little more to the discussion, remember a key point:

RAID is not a backup!!!!

RAID protects against just one thing, hard drive failure.  That is it.  That is not necessarily even the most likely failure, just one of the common ones.  Your OS could thrash your entire array.  Your RAID controller could thrash your entire array (actually saw this happen to someone).  You could accidentally delete/overwrite/format your own data (did this to myself once, fortunately the data loss was not very large and could be recreated with work).  A virus could corrupt all your data (saw someone do this to their work group's network mounted drive, lots of unhappy campers).  And so on.

Now, RAID is probably better than not backing up at all.  And similarly if it is something that happens automatically whereas another backup option is one you must manually do and frequently don't then it has benefit.  But it really isn't intended as, nor does it function particularly well as a backup.  It only protects you from hard drive failure, and that is only one threat to the data.

And it is certainly worth consulting this site to get one's mind in the right place about backing up:

http://www.taobackup.com/

Ken