Tape planning: Example 1

Imagine the case with the following features:

• full backup size is F_GB
• average size of incremental backups is I_GB
• average size of differential backups is D_GB
• compression level provides CL average reduction coefficient
• selected tape rotation scheme is Tower of Hanoi with four levels
• tape options are the following:
• the Use a separate tape set option is selected
• the Always use a free tape: For each full backup option is cleared
• the Always use a free tape: For each incremental backup option is cleared
• the Always use a free tape: For each differential backup option is cleared
• tape size is T_GB.

The Tower of Hanoi scheme with four levels (A, B, C, and D) specifies the following line of backups on the tapes before the first backup will be deleted: D (full), A, B, A, C, A, B, A, D, A, B, A, C. The specified tape options do not require using a free tape for any backup, so the backup line will be automatically split and continued on a new tape when the end of the current tape is reached. There is one tape set to calculate.

Total number of required tapes = round up ((2*F_GB + 6*I_GB + 5*D_GB) * CL / T_GB) + 1.

The above described ToH Example 1 is based on the five-level Tower of Hanoi backup scheme with the same tape options. Its backup line was the following: E (full), A, B, A, C, A, B, A, D, A, B, A, C, A, B, A, E, A, B, A, C, A, B, A, D.

Total number of required tapes = round up ((2*F_GB + 12*I_GB + 11*D_GB) * CL / T_GB) + 1 = round up ( (2*320 + 12*16 + 11*40) * 1 / 400 ) + 1 = round up ( 3.18 ) + 1 = 5 (tapes).