Your system backups are an integral part of your security policy. Not only are they useful when the system goes down, but can be helpful in and investigation (see below). One thing to consider is how long to keep your backups. If an intruder gains access to the system and does nothing for a month, do you have a clean backup from before the break-in? Do you have a copy of a clean system?
In one company I was in, we had five tapes for each machine, one for each day of the work week. We then got a tape loader that could hold enough for two weeks. However, each August there was a company shut down for three weeks. Several people from the IS department as well as some people in sales and customer service continued to work through the vacation. Therefore, regular backups were done. What would happen if someone came back from the three week vacation to find a file missing? There is no backup old enough to find the file!
In addition to the security aspects, doing regular backups is an integral part of administering your
system. For details on backup strategies, see the
section on backups under Basic Administration.