I'm not a fan of tapes; they are more subject to media wear than hard drives during read and writes, and are more susceptible to damage from dust as well. They are also much slower and cumbersome to find a particular file than hard drives. After numerous tape failures and other problems, the company I worked for built a couple of RAID5 servers with docks for removable IDE drives so that the company data was mirrored on two RAID5 arrays, with critical data being backed up to removable hard drives and taken off-site in a rotation. It was much faster and convenient than tapes, and had better reliability as well.
I'll just expand on Jonathan's response a bit.
Tapes are good for long term storage if you feel relatively certain that you won't need to restore from backup. To avoid that, I'd actually recommend to keep the "live" data on a RAID solution, too.
If RAID 5+1 (which is what Jonathan is describing here) seems to expensive, try going for RAID 6 instead, at least if you're going to be using many drives, since that increases the likelyhood of a failure. While RAID 5 has single parity, RAID 6 has two separate parity sets.
I also recommend that you try to get a system that supports hot spares, so that the RAID controller can automatically fail over to an available disk and rebuild the array, and you can get that replacement disk at leisure without worrying too much about a second disk failure.
Although Wikipedia often gets some flack because information be inaccurate, the
article on RAID is informative while containing at least half-decent illustrations.
At work, we use RAID 1+0 (AKA "RAID 10"), which is the optimal compromise between performance and stability for our daily needs. Our backup solution uses three separate RAID 5 sets (not mirrored, but independent data).
We have considered purchasing storage solutions from e.g.
NetApp, HP or IBM, but they are all a bit too pricey for us.
YMMV.