GFS Rotation Schedule
GFS (short for Grandfather-Father-Son).
The most commonly used media rotation schedule is "Grandfather-Father-Son."
GFS has an hierarchical structure.This scheme uses daily (Son), weekly
(Father), and monthly (Grandfather) backup sets.
Four backup media are labeled for the day of the week each backs up. For
example, Monday through Thursday. Typically, incremental/differential
backups are performed on the "Son" group of media. This media is reused
each week on the day matching its label. A set of up to five weekly backup
media is labeled "Week1," "Week2," and so on.
Full backups are recorded weekly, on which day that a "Son" media is not
used. The "Father" media is reused monthly.
The final set of three media is labeled "Month1," "Month2," and so on,
according to which month of the quarter they will be used. This
"Grandfather" media records full backups on the last business day
of each month and is reused quarterly.
Each of these "media" may be a single medium or a set of mediums,
depending on the amount of data to back up. A total of 12 media
sets are required for this basic rotation scheme, allowing for a
history of two to three months.
See also: Tower of Hanoi, Backup Rotation