Network Data: Normal Backups
A normal backup — also called a full backup — is the basic type of backup. In a normal backup, all files in the backup selection are backed up regardless of whether the archive bit has been set. In other words, the files are backed up even if they haven’t been modified since the last time they were backed up.
When each file is backed up, its archive bit is reset, so backups that select files based on the archive bit setting won’t back up the files.
When a normal backup finishes, none of the files in the backup selection have their archive bits set. As a result, if you immediately follow a normal backup with an incremental backup or a differential backup, no files will be selected for backup by the incremental or differential backup because no files will have their archive bits set.
The easiest backup scheme is to simply schedule a normal backup every night. That way, all your data is backed up on a daily basis. Then, if the need arises, you can restore files from a single tape or set of tapes. Restoring files is more complicated when other types of backups are involved.
Do normal backups nightly if you have the tape capacity to do them unattended: that is, without having to swap tapes. If you can’t do an unattended normal backup because the amount of data to be backed up is greater than the capacity of your tape drive(s), you have to use other types of backups in combination with normal backups.
If you can’t get a normal backup on a single tape and you can’t afford a second tape drive or a tape changer, take a hard look at the data that’s being included in the backup selection. Be sure that you are not backing up a large amount of static data.
This data was necessary because network users needed it for research purposes, but the data was read-only. Even though the data never changed, it was being backed up to tape every night, and the backups required two tapes. After this data was removed from the cycle of nightly backups, the backups were able to squeeze onto a single tape again.
If you remove static data from the nightly backup, make sure that you have a secure backup of the static data on tape, CD-RW, or some other media.