Defining a Rotation Scheme
One of the key elements of any backup plan is to develop a media rotation scheme that protects your data at least once a day. The best rotation schedule is one that provides you with a long, deep and varied history of file versions (as opposed to a tape-a-day scheme, for instance, that merely overwrites data from the day previous.)
Protecting your data at least once per day is essential. However, the cost or time required to do a full backup everyday can be impractical, especially for companies with vast amounts of data. Many users therefore will do an incremental or differential backup on most days. Differential backups back up every file that has changed since the last full backup. Incremental backups back up only files that have changed since the previous incremental or full backup. Finding a specific file to restore is more difficult with these partial backups since it may be on one of several tapes.
At least once per week a full backup should be performed. This will provide a recent record of all files, minimising the number of tapes to search for a recent copy of a single file. Full backups also create a level of redundancy for most files, duplicating exactly any files that have changed during the week as well as duplicating any files that exist on the prior week's full backup.
Here, we outline two popular rotation schemes that are offered as configurable backup patterns by most backup application software, the "Grandfather-Father-Son" and "Tower of Hanoi" schemes. Both offer a great depth of file versions; you can choose the one that works for you, or customise one to your own needs. Then, make sure to put it into place at all locations and across all types of data on every platform.