User Guide

The Custom backup scheme enables you to specify a backup schedule and retention rules to define a

desired tape rotation. Use this scheme, when the Grandfather-Father-Son and the Tower of Hanoi

schemes’ usage is not enough. For example, if the full size of protected data is considerably less than

the size of a tape, the best choice is to use the Custom backup scheme with regular

daily/weekly/monthly full backups, some simple retention rules, and tape options by default.

Criteria of the choice

Every time you are about to design a tape rotation scheme for a backup policy/plan to be created,

you ought to come from the following arguments:

 full size of the data to protect

 approximate size of the daily changes of data

 approximate size of the weekly changes of data

 requirements for the backup scheme (frequency, performance and duration of backup

operations)

 requirements for keeping backups (minimal/maximal period of backup keeping; need to store

tape cartridges off-site)

 capability of the tape library (number of drives, loaders, slots and available tapes; capacity of

tapes)

 requirements for performing data recovery (maximal duration)

You need to analyze every argument that is relevant for your case and select the main criteria for the

choice. Then choose a backup scheme and specify the tape options.

Note, that any backup scheme in combination with different tape options will have quite different

results for efficient use of both tapes and devices.

Case to analyze

Suppose you need to automate a tape rotation for the case if:

 the full size of the data to protect is approximately 320 GB

 the approximate size of daily changes of data is about 16 GB

 the approximate size of weekly changes of data is no more than 40 GB

 tape capacity is 400 GB.

Let’s analyze the results of a combination of GFS and ToH schemes with different tape options for the

case.

All the below analyzed examples are a simplistic approach to a real case, but provide you with a

general conception of backup distribution onto tapes.

Legend for the case example figures

Any daily/incremental backup (16 GB) is shown in the figures as a green rectangle: .

Weekly/differential backups (40 GB) are displayed as a blue rectangle:

Any full monthly backup (320 GB) is drawn in orange:

A whole tape (400 GB) is drawn as a gray rectangle: