Since a hard disk is many times the size of a floppy disk, it takes many floppies to back up a hard disk. This set of disks is called a backup set. Each disk in a backup set is identified by a disk name consisting of a backup set name and a volume number. If the backup set is called BACKA, the first disk in the backup set would be called BACKA.$01, the second would be BACKA.$02, and so forth.
The disk name is written on the disk by The Vault and checked during subsequent backups to make sure the proper disk has been inserted. You should also label the floppy the same way so you can easily identify it later.
As mentioned in Section ![[*]](crossref.png)
, keeping only one backup
set is not enough to provide full protection. If you are backing up
the hard drive with your only backup set in the floppy drive and you
discover an error with a file on the hard disk or the hard disk
crashes, you are out of luck, for there is no complete backup set from
which you can restore your hard disk files.
Thus, you should have two backup sets for full backups, and they should be rotated. The first time you do a full backup, you should use set 1. The next time, use set 2, the next time, set 1 again, and so on.
For even greater protection, you might consider having a third ``disaster backup set" which you only write occasionally and then put into safe storage, preferably at another location. Not only does this provide protection again disasters such as fire, but it also offers some protection against hidden errors. Sometimes a file might become corrupted but the error not discovered until weeks later when the file is used. If you have been faithfully backing up your hard disk and rotating among the two backup sets for full backups, the corrupted file will eventually be propagated to all of your backup disks, and when you go to recover it, all you will find is several copies of the same bad file.
To successfully rotate your backup sets, you must remember which one was used last. If you keep your backup disks in a box, put the most recently used set in the front and you will never forget which one was used last. If you do get mixed up, you can look in the history file on the hard disk (_BACKUP.HST or _BACKUP.CTL on the floppy disk).
In addition to the full backup sets, you need two incremental sets consisting of two or three disks each. Every day, before shutting off the computer, do a daily incremental backup. This will usually add only a small amount of data to the incremental set. After repeated daily backups, the incremental set will eventually fill up. At this time, you can do one of two things. If the hard disk has changed significantly since the last full backup, then do another full backup. Otherwise, perform a cleanup incremental backup on the second set and rotate the sets so that the set on which you just performed the cleanup incremental is the one on which future daily incrementals will go. The old incremental set is then no longer needed and should be kept idle until the time comes for another cleanup incremental.