System Administration Guide: Devices and File Systems

Guidelines for Scheduling Backups

The following table provides guidelines for scheduling backups. For additional backup schedule considerations, see Considerations for Scheduling Backups.

Table 24–6 Guidelines for Backup Schedules

File Restoration Need 

Backup Interval 


To restore different versions of files (for example, file systems that are used for word processing) 

Do daily incremental backups every working day. 

Do not reuse the same tape for daily incremental backups.

This schedule saves all files modified that day, as well as those files still on disk that were modified since the last backup of a lower level. However, with this schedule, you should use a different tape each day because you might otherwise be unable to restore the needed version of the file.  

For example, a file that changed on Tuesday, and again on Thursday, goes onto Friday's lower-level backup appearing as it did Thursday night, not Tuesday night. If a user needs the Tuesday version, you cannot restore it unless you have a Tuesday backup tape (or a Wednesday backup tape). Similarly, a file that is present on Tuesday and Wednesday, but removed on Thursday, does not appear on the Friday lower-level backup. 

To quickly restore a complete file system 

Do lower-level backups more frequently. 


To back up a number of file systems on the same server 

Consider staggering the schedule for different file systems. 

This way you're not doing all level 0 backups on the same day. 

To minimize the number of tapes used 

Increase the level of incremental backups that are done across the week.  

Only changes from day to day are saved on each daily tape. 


Increase the level of backups that are done at the end of the week. Put each day's and week's incremental backups onto the same tape. 

Only changes from week to week (rather than the entire month) are saved on the weekly tapes. 


Put each day's and week's incremental backups onto the same tape. 

To do so, use the no rewind option of the ufsdump command, such as specifying /dev/rmt/0n.