This scheme involves performing a full backup of the entire system once a week, along with a daily incremental backup of only those files that have changed in the previous day, and it begins to resemble what a sysadmin of a medium to large system would traditionally use.
This backup scheme can be advanced in two ways. In one way, each incremental backup can be made with reference to the original full backup. In other words, a level 0 backup is followed by a series of level 1 backups. The benefit of this backup scheme is that a restoration requires only two tapes (the full backup and the most recent incremental backup). But because it references the full backup, each incremental backup might be large (and grow ever larger) on a heavily used system.
Alternatively, each incremental backup could reference the previous incremental backup. This would be a level 0 backup followed by a level 1, followed by a level 2, and so on. Incremental backups are quicker (less data each time), but require every tape to restore a full system. Again, it is a classic trade-off decision.
Modern commercial backup applications such as Amanda or BRU assist in organizing the process of managing complex backup schedules and tracking backup media. Doing it yourself using the classic dump or employing shell scripts to run tar requires that the system administrator handle all the organization herself. For this reason, complex backup situations are typically handled with commercial software and specialized hardware that are packaged, sold, and supported by vendors.
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