The following table shows a schedule where each weekday tape contains only the files that changed since the previous day. In addition, each Friday's tape contains all files changed since the initial level 0 backup at the beginning of the month.
Table 23–11 Daily Incremental, Weekly Cumulative Backup Schedule
Floating |
Mon |
Tues |
Wed |
Thurs |
Fri |
|
---|---|---|---|---|---|---|
1st of Month |
0 |
|
|
|
|
|
Week 1 |
3 |
4 |
5 |
6 |
2 |
|
Week 2 |
3 |
4 |
5 |
6 |
2 |
|
Week 3 |
3 |
4 |
5 |
6 |
2 |
|
Week 4 |
3 |
4 |
5 |
6 |
2 |
The following table shows how the contents of the tapes can change across two weeks with the daily incremental, weekly cumulative schedule. Each letter represents a different file.
Table 23–12 Contents of Tapes for Daily Incremental, Weekly Cumulative Backup Schedule
Mon |
Tues |
Wed |
Thurs |
Fri |
|
---|---|---|---|---|---|
Week 1 |
a b |
c d |
e f g |
hi |
a b c d e f g h i |
Week 2
|
j k l |
m |
n o |
p q |
a b c d e f g h i j k l m n o p q r s |
With this schedule, you need at least 9 tapes if you want to reuse daily tapes, which is not recommended. Preferably, you need 21 tapes if you save weekly tapes for a month: one tape for the level 0, 4 tapes for the Fridays, and 4 or 16 daily tapes.
1 tape for the level 0 backup
4 tapes for all the Friday backups
4 or 16 daily tapes
If you need to restore the complete file system, you need the following tapes:
The level 0 tape
The most recent Friday tape
All the daily tapes since the last Friday tape, if any