The minimum number of days we are guaranteed to have is called the roll-back period.
SCHEME HANOI TOWERS ARCHIVE
The number of days we can go back in the archive is different on different days. Having four backups, we could recover data as of today, yesterday, half a week, or a week ago. The scheme allows for efficient data storage: more backups accumulate toward the current time.
SCHEME HANOI TOWERS FULL
Here is how the archive looks on day 8, a day before creating a new full backup. First-level (1) backups are incremental.Ī cleanup mechanism ensures that only the most recent backups of each level are kept.Backups of intermediate levels (2, 3) are differential.Last-level (in this case, level 4) backups are full.Shaded numbers denote backup levels.īackups of different levels have different types: This is how the first 14 days (or 14 sessions) of this scheme's schedule look. Backups of intermediate levels are differentialīackup type: Full/Differential/Incremental Full/Differential/Incremental - backups of different levels will have different types:.This is the default selection for cases when a tape drive is selected as a backup location. Always full - all levels of backups will be full.Specifies what backup types the backup levels will have Calculated automatically, depending on the schedule parameters and the numbers of levels you select. The guaranteed number of sessions that one can go back in the archive at any time. See the example stated below for details. In the discussion below, "days" can be replaced with "scheduled sessions". Thus, complex schedules specify the sessions on which the scheme should run. During the specified days the task will be repeated every 2 hours from 10 AM to 10 PM). Setting up schedule parameters allows for the creation of simple schedules (example of a simple daily schedule: a backup task will be run every 1 day at 10 AM) as well as more complex schedules (example of a complex daily schedule: a task will be run every 3 days, starting from January 15. Set up a daily, weekly, or monthly schedule. You can set up the following parameters of a Tower of Hanoi scheme. One backup of each level is stored at a time.Next-level backups are twice as rare as previous-level backups.Up to 16 levels of full, differential, and incremental backups.Tower of Hanoi scheme Tower of Hanoi scheme
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