Acronis Backup & Recovery 10 Adv WS TIDLBPDES Manuale Utente

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16 weekly sessions so it ensures the roll-back period equal 112 days. Tape rotation for the second
case includes 128 daily sessions, i.e. it allows the roll-back period equal 128 days.

Each additional level doubles not only the number of sessions but also the oldest backup age.

Let’s return to the analyzed case described in the Case to analyze section, and suppose the ToH
settings are the following:

•

Schedule:

Start the task every 1 day at 11:00 PM. Repeat once.

•

Number of levels: 5

The Tower of Hanoi scheme with five levels ensures the roll-back period equal 16 days, but it
simplifies an analysis of the scheme usage examples. Let’s designate the backups of the levels with
numbers from 1 to 5 by letters A, B, C, D, and E respectively. Then the rotation template for the
backup sequence in the archive is the following: E-A-B-A-C-A-B-A-D-A-B-A-C-A-B-A. In the five-level
ToH scheme all the backups on the 1st level (A) are incremental, on the 5th level (E) – full, and other
backups on levels 2, 3, and 4 (B, C, and D) are differential.

Tape rotation for the ToH scheme substantially depends on the tape options, whose default settings
do not always provide optimal usage of tapes and the whole tape library.

The goal is to choose the tape options requiring the minimal number of tapes in the rotation.

There are analyzed examples showing how the ToH scheme can be combined with different tape
options in the following sections:

•

ToH Example 1 (p. 148). The Use a separate tape set option is selected. All the Always use a free
tape options are cleared. It requires 5 tapes in rotation.

•

ToH Example 2 (p. 149). The Use a separate tape set option is selected. The Always use a free
tape: For each full backup option is selected. The other Always use a free tape options are
cleared. It requires 4 tapes in rotation.

•

ToH Example 3 (p. 150). The Use a separate tape set option is selected. All the Always use a free
tape options are selected. It requires 7 tapes in rotation.

ToH Example 2 requires 4 tapes, which is the minimum for the case. So its tape options settings are
the best in comparison with options for other examples.

ToH Example 1

Suppose, the backup plan has the following tape options:

•

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.

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