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The solution is tape rotation. Do not use a different tape each day. Instead, reuse tapes from previous months and weeks. We will look at some simple rotations, such as weekly, along with some rather complicated schemes.

Weekly Rotation

In a weekly rotation, you use a different backup tape or tapes for each day of the week. Weekly rotations are the simplest to understand and set up. You first assign a tape to each weekday and label the tape with the name of the day. You have five tapes, and you overwrite each tape as the day of the week comes again. The furthest you can go back to do a restore is one business week. On Friday, before the backup, you can go back to any day for one week, but no further.

Monthly Rotation

Rotating tapes on a monthly basis allows you to restore data for an entire month. Managing this type of backup scheme is more complicated because you must keep track of many more tapes. A straightforward solution is to assign 31 tapes and do a full backup each day. This becomes unwieldy if a full backup takes many tapes. For example, a thousand-user corporation’s e-mail, file, and print servers can take multiple high-capacity DLT tapes per session.

Most of your restore requests will be reported shortly after the file is accidentally deleted or corrupted. Take your typical user who accidentally deletes his home directory. Using a GUI interface, this is as easy as rightclicking a folder and then left-clicking Delete. The user will immediately call network support and plead for quick rescue. In this case, you only have to go back to the previous day’s tape. To plan for this scenario, have daily backups that go back a week. Supplement this with a weekly backup for an entire month.

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