## Tape planning: Example 1Imagine 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). |