There are several different things you can do. First, you need to determine what your backup retention policy is for the company. Also, it would be helpful to know how much data you normally back up with an average Full and Differential backup.
I would recommend the following: (depending on your hardware)
One Drive - no autoloader
Use 1 tape for Full backup (1 tape per week for your Full)
Use 1 tape for Differential backup (1 tape per week of differentials)
Once you determine how long you want to retain the data, you can determine how many tapes to use. In my environment, we keep 6 weeks of Full media and 3 weeks of Diff media.
You will probably want to configure two media sets - Full and Diff
In the example above, I would set overwrite protection on my Full set for 5 weeks (will be overwritten on the sixth week). I would also set the overwrite protection on the Differential set to 2 weeks (overwritten on the 3rd week)
You may also want to consider creating a DR (Disaster Recovery) Tape periodically that you keep in a safe location. Personally, I create a DR every week and store it offsite with a six week rotation in addition to a 3 week rotation for my Full backup which remains onsite.
Hope this helps.
