An Introduction to Tape Backup - Tape Rotation...
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3. Tape Rotation
The ideal tape backup solution would involve using a new tape for each backup. This means purchasing a new tape for every day of your business's operations. This is hardly cost-effective for your business. Tape is cheap, but not that cheap!
This is why we speak of tape rotation. Tape rotation means to reuse tapes from previous backups. The simplest tape rotation scheme is to have one tape for each day of the working week. Tapes are labeled Monday, Tuesday, Wednesday, Thursday and Friday.
You can restore data from any one of the tapes in your library, or in this case, any day in the past the week. This strategy requires only five tapes, but only provides one week's data backup history.
4. Grandfather-Father-Son - A Case Study
The grandfather-father-son schedule is the most widely used method, and involves backing up data in the following way:
daily - on the "son tapes"
weekly - on the "father tapes"
monthly – on the "grandfather tapes"
This system is far more powerful than the five-tape rotation, but requires more tapes.
This strategy provides you with the ability to restore data from the last week, plus any Monday over the last month, plus any month for as many monthly tapes as you have. Variations on this scheme are available, and provide a trade-off between the number of tapes required, and the number of monthly tapes available.
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