Installation guide

To integrate incremental backups into your file backup schedule, you need
to balance the time and tape space required for backup against the amount
of time it could take you to restore the system in the event of a system
failure. For example, you could schedule backup levels following the 10-day
sequence:
0123456789
On the first day you save an entire file system (level 0). On the second day
you save changes since the first backup and so on until the eleventh day
when you restart the sequence. This makes the amount of time spent and
data saved on each backup relatively small each day except the first;
however, if a system failure on the tenth day requires that you restore the
entire system, you must restore all ten tapes.
Most systems follow some variant of the common Tower of Hanoi backup
schedule. Once a month you make a level 0 dump to tape of all the
regularly backed up file systems. Then once a week, you make a level 1
dump to start a daily sequence of:
...3 2 5 4 769899...
If you do backups only once a day on the weekdays, you end up with a
monthly backup schedule as follows:
01325413254...
This schedule, although slightly complex, requires that you restore at most
four tapes at any point in the month if a system failure corrupts files. Of
course, doing a level 0 dump daily requires that you restore at most one
tape at any point, but requires a large amount of time and tape storage for
each backup. On most days in the Tower of Hanoi schedule, very little time
and tape storage are required for a backup.
11.3.2 Performing a Full Backup
You should set up a schedule for performing a full backup of each file
system on your entire system, including all the system software. A
conservative schedule for full system backups is to do one with each normal
level 0 dump (using Tower of Hanoi, once a month), but you can set any
schedule you like within the reliability of your storage media, which is
about two years for magnetic tapes. To back up your file system, use the
dump command, which has the following command syntax:
dump options filesystem
The
options parameter specifies a list of flags and their arguments and
the
filesystem parameter specifies the file system to be backed up. You
should specify the file system with a full pathname. The dump command
can back up only a single file system at a time, but there may be several
dump processes simultaneously writing files to different tape devices.
Administering the Archiving Services 11–11