1. Capacity.

Select a tape drive that has sufficient capacity to store your backups. Tape drives are able to compress data so that more data may fit on tape, which is why manufacturers specify both a native capacity and a compressed capacity, usually with a compression ratio at 2:1. However, highly-compressed files such as those in video and sound formats are hardly compressible at all. For this reason, do not heed specified compressed capacity when choosing a tape drive.

A good way to determine size of backup job after compression is to study logs of past backups. If these are unavailable, it is safe to assume that data can be compressed at a ratio of 1.4:1, unless hard drive contains an usually large number of highly-compressed files.

2. Transfer rate.

The transfer rate of tape drive is becomes important when there is limited "window of opportunity" in which backup jobs may run. It is often desirable for backups to take place during night when network use is at its lowest. Select a tape drive that is capable of completing a backup job within your window of opportunity. For instance, to back up 400GB per night, you will require a transfer rate of about 30GB/hour.

Typically, restore process involves reinstalling operating system and configuring all physical storage to their original settings before restoring data and settings. Rebuilding system in this way is a time-consuming and often problematic task, causing many headaches for administrators and technical staff.