Data backup is very a famous term in systems administration and nearly any business or home users are consider it.
For SMB or enterprises environment Lukas and I had a small conversation about this issue along time ago after three years experience and new business demands I can share my experience which I'v gained during that.
there is a variety of tape drives like 4mm, VXA, LTO and more but these are popular.
Every type has it's own features for certain period of time e.g 4mm can backup 45GB within more than 3 hours that period(2005) as I remeber 45GB was a huge amount of data.
LTO2 can backup up to more than 400GB within much less time compared to 4mm, LTO features are more needed these days as I said before business demands.
I'll mention some of the LTO2 HH tape drive features:
-Capacity: 200/400 GB (native/compressed)
-Transfer rates of up to 172.8 GB/Hr (assumes 2:1 data compression)
If you look to todays needs this is the right solution for you for SMB which holding up to 100 users with all the data needed to run your business and employee documents.
I am sure there's alot more type or opinions from other people who used different types, Please share it.
Picture used from http://www.smallbusinesscomputing.com