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2
2 days
1 to 2 days
1 day
3
4 days
2 to 5 days
2 days
4
8 days
4 to 11 days
4 days
5
16 days
8 to 23 days
8 days
6
32 days
16 to 47 days
16 days
Adding a level doubles the full backup and roll-back periods.
To see why the number of recovery days varies, let us return to the previous example.
Here are the backups we have on day 12 (numbers in gray denote deleted backups).
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2
3
4
5
6
7
8
9
10 11 12
4
1
2
1
3
1
2
1
4
1
2
1
A new level 3 differential backup has not yet been created, so the backup of day five is still stored.
Since it depends on the full backup of day one, that backup is available as well. This enables us to go
as far back as 11 days, which is the best-case scenario.
The following day, however, a new third-level differential backup is created, and the old full backup is
deleted.
1
2
3
4
5
6
7
8
9
10 11 12 13
4
1
2
1
3
1
2
1
4
1
2
1
3
This gives us only a four day recovery interval, which turns out to be the worst-case scenario.
On day 14, the interval is five days. It increases on subsequent days before decreasing again, and so
on.
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
The roll-back period shows how many days we are guaranteed to have even in the worst case. For a
four-level scheme, it is four days.
6.2.10.6
Custom backup scheme
At a glance
Custom schedule and conditions for backups of each type
Custom schedule and retention rules
Parameters
Parameter
Meaning
Full backup
Specifies on what schedule and under which conditions to perform a full backup.
For example, the full backup can be set up to run every Sunday at 1:00 AM as
soon as all users are logged off.
