Type of restore required . If so, a large-capacity tape drive might suit you. If you have ever had to restore just one file from a tape backup, you know that finding the correct file can take hours. If you have to meet both needs, you might want to consider a mix of backup types, using both sequential and random access devices. Speed of backup and restore .
Tape is notoriously slow.
Even with recent advances, tape is not very fast compared with a hard disk. Tape capacities have not kept up with the incredible progress in the size of hard disks. Plan to back up the entire system regularly and crucial files frequently, and you can easily calculate the capacity you will need. Be careful about how the manufacturers state capacity. The industrial-strength drives such as Exabyte usually list their native capacity.