Creating a Backup Schedule

When to do full backups

One possible backup schedule is to store your entire system to tape at the end of each work day. The benefit of this schedule is that in a recovery situation, you or the system operator must handle only one tape set. The disadvantage is that, since all files (including those that have not changed) are backed up every day, the amount of time and media needed to complete the backup increases greatly.

When to use cumulative backups

Another strategy is to perform a full backup once per week, and partial cumulative backups on all other work days. This strategy reduces both time and media usage. In a cumulative backup, the date is always the date of the last full backup and uses the "greater than or equal" form ;DATE>=mm/dd/yy.

Following a cumulative backup stategy, you will need to handle only two store tape sets to perform a full system recovery: the most recent full backup set and the most recent partial backup set.

Figure 10-1 Cumulative Backup Schedule

When to use incremental backups

In an incremental backup strategy, you perform a full backup once per week and partial backups on all other workdays. However, since the date of each partial backup is the date of the last partial backup (not the date of the last full backup), only those files which have changed are copied to tape.

The principal advantage to the incremental backup strategy is that it uses the smallest amount of time and media. The disadvantage is that, in the event of system recovery, you must restore each tape set from the most recent full backup through the most recent partial backup.

Figure 10-2 Incremental Backup Schedule