Just to add:
After surfing few sites and researching about the Tape Backup, here are some of the advantages I could list down over disk-based technologies for long-term data storage
1. High capacity as LTO tape cartridges can now store up to 6.25TB on a single tape.
2. Fast performance and Lower cost per GB (average cost of $.01/GB)
3. Reduced energy costs as Tape drives use less power and generate less heat than disk drives,
4. Portability & Greater reliability as the error rate of tape technology is superior to that of disk
5. Better longevity, good Scalability and Compatibility