Acronis Backup & Recovery

Tape planning: Example 2

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 Custom with the following settings:
  • full backup – every 10 days
  • differential backup – every 2 days
  • incremental backup – every 1 day, every 6 hours
  • retention rules: delete backups older than 5 days
• 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 selected
  • 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 case defines the line of backups that consists of two sections. The figure below shows the sections at the moment before the first backup will be deleted. In the figure the full, differential and incremental backups are designated as orange, blue and green rectangles respectively.

At the moment some backups are deleted by the Cleanup task. Deletion of the outdated backups painted in dark colors is postponed, as these backups are basic for the actual backups.

As an exact correlation between the tape size and backup’s size is unknown, it is impossible to determine number of the tapes that will be free after the deletion. So the calculation ignores this probability.

Tape set 01 should contain (round up (( F_GB + 4*D_GB + 5*7*I_GB) * CL / T_GB)) tapes to store the backups. Tape set 02 needs (round up (( F_GB + 1*D_GB + 7*I_GB) * CL / T_GB)) tapes. The sum of the calculated values gives the total number of tapes required for the case.