“Know here the different kinds of data backup rotation schemes and conclude which suits best for your environment.”
Before knowing the types of backup rotation schemes, let’s know what is backup rotation scheme briefly.
A backup rotation scheme is a data backup mechanism that diminishes the amount of storage media required by the concept of re-use.
This scheme defines in what ways and conditions each piece of removable storage is used for a backup and how long it is reserved once it is backed up.
Nowadays, numerous different practices have been developed to balance data preservation and restoration requirements with the price tag of additional data storage media.
- FIFO (First-In-First-Out)
This backup scheme saves new or modified data onto the firstborn (media that holds the oldest and least useful data backup) in the system. Executing a daily backup onto a set of 14 storage media, with a backup depth of 14 days is the agenda of FIFO.
It’s the simplest backup rotation scheme and is typically the first one to strike the mind. The advantage of this scheme is it preserves the stretched (possible) tail of daily backups. It is very useful when your archived data is insignificant, if it is separately taken from the short-range data backup, or if data before the rotation period is inappropriate.
However, there is a probability of data loss in this scheme since it falls short of detecting the error. For instance, an error gets introduced into the data and it is not identified until several cycles of backups and reviews. Finally, by the time the error is spotted, all the backup files enclose the error.
- Grandfather-Father-Son
Grandfather-father-son is a common backup rotation scheme for media. It has three or more backup cycles, daily, weekly, and monthly.
The daily backups are swapped on a daily basis via the FIFO system. The weekly backups are rotated on a weekly basis, and the monthly backups are done on a monthly basis.
Additionally, trimester, bi-trimester, and annual backup schemes are also available. Every so often few of these backups are eliminated from the site for the purpose of protection and disaster recovery.
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- Tower of Hanoi
The Tower of Hanoi backup rotation method is more complex compared to the above two schemes. It is based on the arithmetic of the Tower of Hanoi riddle, which uses a recursive technique to enhance the backup cycle.
Every single tape matches a disk in the puzzle, and each disk movement matches a diverse peg related to a backup in that tape. Thus, the first tape is employed every other day (1, 3, 5, 7, and so on), the second tape is employed every fourth day (2, 6, 10, and so on), and the third tape is employed every eighth day (4, 12, 20, and so on). So, a set of X tapes (or any other media) allow backup for 2X−1 days before the last set is reprocessed.
- Incremental Media
This method has numerous variants and labels. A set of numbered media is employed till the finale of a cycle. Then the cycle recurrences using media numbered similar to the former cycle but with an increment of one.
The lowermost numbered tape from the earlier cycle is discharged and kept forever. Thus, you can access every backup for one cycle and one backup per cycle before that.
This system has a plus point in that it ensures even media wear but calls for a schedule to be pre-calculated.
Apart from the above, there are many other backup rotation schemes like Round Robin, Round Robin with archiving, N week Daily, Daily + N Weekly, etc. So, know each of them in detail before you implement them.
