All about Backup

Tower of Hanoi Rotation Schedule

Tower of Hanoi got its name from an ancient Chinese game using recursive techniques. In the game, you move a stack of disks from one of the pegs to another peg and a smaller disk can only be placed on a larger disk.
Like the game, many multiple media sets are rotated through in incremental/differential and full backups. It uses more media sets than GFS for increased safety.In this schedule, one media set "A" is used every other backup session (daily sessions in this example).Start Day 1 with "1" and repeat every other backup (every other day).

The next media set "B" starts on the first non-"A" backup day and repeats every fourth backup session. Media set "C" starts on the first non-"A" or non-"B" backup day and repeats every eighth session. Media set "D" starts on the first non-"A," non-"B," or non-"C" backup day and repeats every sixteenth session. Media set "E"alternates with media set "D."

Media set Week's number
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
A x x x x x x x x x
B x x x x x
C x x
D x
E x

With each additional media set added to the rotation scheme, the backup history doubles.The frequently used media sets have the most recent copies of a file, while less frequently used media retain older versions. This schedule can be used in either a daily or weekly rotation scheme. The decision regarding the frequency of rotation should be based on the volume of data traffic. To maintain the required history of file versions, a minimum of five media sets should be used in the weekly rotation schedule, or eight for a daily rotation scheme. As with the Grandfather-Father-Son rotation scheme, media should be periodically removed from the rotation for archive purposes.

See also: Round Robin, Backup Rotation

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