A sixty meter DAT tape has a nominal capacity of 1300 megabytes. For everyday use this means you will typically achieve capacities anywhere from 700 to 1250 MB. Using a ninety meter tape you can expect to get fifty percent more data on a tape (1.9 gigabytes instead of 1.3 GB). Drives using the DDS-2 format support 120 meter tapes for an uncompressed data capacity of about four gigabytes.

If you use a drive with hardware compression, you can roughly double the capacity of your tapes. Your tape's actual capacity will depend largely upon how well the data you are copying compresses. Text compresses well, for example, but applications do not.

If you back up many small files or back up files over a network, your tape's actual capacity will also decrease.

Retrospect only requests a new tape for one of three reasons:

The tape drive reports the current tape is full.

An error occurred while writing to the tape. Open the log to see if an error occurred.

You selected Skip or Missing while configuring a backup set, or you are performing a new backup.