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Operational and Organizational Security: Policies and Disaster Recovery• Chapter 12 733

Rotation Schemes

It is important to keep at least one set of backup tapes offsite, so that all of the
tapes are not kept in a single location. If backup tapes were kept in the same loca-
tion as the servers that were backed up, all of the data (on the server and the
backup tapes) could be destroyed in a disaster. By rotating backups between a dif-
ferent set of tapes, data is not always being backed up to the same tapes, and a pre-
vious set is always available in another location.
A popular rotation scheme is the Grandfather-Father-Son (GFS) rotation,
which organizes rotation into a daily, weekly, and monthly set of tapes.With a GFS
backup schedule, at least one full backup is performed per week, with differential
or incremental backups performed on other days of the week.At the end of the
week, the daily and weekly backups are stored offsite, and another set is used
through the next week.To understand this better, assume a company is open
Monday through Friday.As shown in Table 12.2, a full backup of the server’s
volume is performed every Monday, with differential backups performed Tuesday
through Friday. On Friday, the tapes are moved to another location, and another set
of tapes is used for the following week.

Table 12.2 Sample Backup Schedule Used in Week

Sunday Monday Tuesday Wednesday Thursday Friday Saturday
None Full Backup Differential Differential Differential Differential, None
with week’s
tapes
moved
offsite

Because it is too expensive to continually use new tapes, old tapes are reused
for backups.A tape set for each week in a month is rotated back into service and
reused. For example, at the beginning of each month, the tape set for the first week
of the previous month would be rotated back into service, and used for that week’s
backup jobs. Because one set of tapes are used for each week of the month, this
means that most sets of tapes are kept offsite. Even if one set were corrupted, the
set up tapes for the previous week could still be used to restore data.
In the GFS rotation scheme, the full backup is considered the “Father,” and the
daily backup is considered the “Son.”The “Grandfather” segment of the GFS rota-
tion is an additional full backup that is performed monthly and stored offsite.The
Grandfather tape is not reused, but is permanently stored offsite. Each of the

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