A dump schedule coordinates the use of tape media so that a minimum number of
tapes are used to provide the maximum amount of backup coverage required.
A typical dump schedule starts with a level 0 backup, sometime at the end of
the week, followed by incremental dumps on successive days in the week.
For example:
Monday Tuesday Wednesday Thursday Friday
|-------|--------|----------|--------|------|
| 2 | 2 | 2 | 2 | 0 |
|-------|--------|----------|--------|------|
This schedule has the advantage of requiring only two sets of tapes. On
Friday, a level 0 backup stores every file on the file system onto one set of
tapes. Then, Monday through Thursday, only the files that have changed or have
been created are stored on a second set of tapes. However, if a file is changed
on Thursday, and the user wants to restore the file to a previous state, the
user can only restore to Wednesday's or the previous Friday's file. This
schedule works well for a system that is small and on which not many changes are
made during the week.
For a larger file system, with many users changing and creating files, the
following schedule might be more appropriate:
Monday Tuesday Wednesday Thursday Friday
|-------|--------|----------|--------|------|
| 8 | 6 | 6 | 2 | 0 |
|-------|--------|----------|--------|------|
This schedule requires five sets of tapes, but the schedule allows users to
change and modify files and back up to any previous day's work if the file is
lost.