System Administration Guide, Volume 1

Tape Requirements

With this schedule, you need six tapes (if you want to reuse daily tapes), or nine tapes (if you want to use four different daily tapes): one for the level 0, four for the Fridays, and one or four daily tapes.

If you need to restore a complete file system, you need the following tapes: the level 0, all the Friday tapes, and the most recent daily tape since the last Friday tape (if any).