Nonrewinding Device Requirement

You must use a nonrewinding device for Backup backups. Backup writes a file mark on a volume at the end of each backup. When the next backup occurs, Backup appends data to the volume based on the position of the file mark.

If the device automatically rewinds the data, the file mark position is lost and the data is overwritten by the next backup; you will be unable to recover the previous backup data at a later date.