User guide

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 Higher density of more recent backups
Parameters
You can set up the following parameters of a Tower of Hanoi scheme.
Schedule
Set up a daily (p. 54), weekly (p. 56), or monthly (p. 58) schedule. 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. During the specified days the task will be repeated every 2 hours from
10 AM to 10 PM). Thus, complex schedules specify the sessions on which the scheme
should run. In the discussion below, "days" can be replaced with "scheduled sessions".
Number of levels
Select from 2 to 16 backup levels. See the example stated below for details.
Roll-back period
The guaranteed number of sessions that one can go back in the archive at any time.
Calculated automatically, depending on the schedule parameters and the numbers of
levels you select. See the example below for details.
Backup type
Specifies what backup types the backup levels will have
 Always full - all levels of backups will be full. This is the default selection for cases
when a tape drive is selected as a backup location.
 Full/Differential/Incremental - backups of different levels will have different types:
- Last-level backups are full
- Backups of intermediate levels are differential
- First-level backups are incremental
Example
Schedule parameters are set as follows
 Recur: Every 1 day
 Frequency: Once at 6 PM
Number of levels: 4
Backup type: Full/Differential/Incremental
This is how the first 14 days (or 14 sessions) of this scheme's schedule look. Shaded numbers denote
backup levels.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
4
1
2
1
3
1
2
1
4
1
2
1
3
1
Backups of different levels have different types:
 Last-level (in this case, level 4) backups are full;
 Backups of intermediate levels (2, 3) are differential;
 First-level (1) backups are incremental.
A cleanup mechanism ensures that only the most recent backups of each level are kept. Here is how
the archive looks on day 8, a day before creating a new full backup.
1
2
3
4
5
6
7
8
4
1
2
1
3
1
2
1