Types of Backups

Types of Backups

All types of backups can be broken into the following categories: . Normal/Full: The full backup backs up all files selected and shuts off

the archive file attribute, indicating the file has been backed up. . Incremental: An incremental backup backs up the files selected if the

archive file attribute is on (files since the last full or incremental back- up). After the file has been backed up, it shuts off the file attribute to indicate that the file has been backed up. Note: You should not mix incremental and differential backups.

. Differential: A differential backup backs up the files selected if the archive file attribute is on (files since the last full backup). Different from the incremental backup, it does not shut off the archive attribute. Note: You should not mix incremental and differential backups.

Backups and System Recovery

. Copy backup: A copy backup is like a normal backup, but it does not shut off the archive attribute. This is typically used to back up the system before you make a major change to the system. The archive attribute is not shut off so that your normal backup procedures are not affected.

You decide to back up the entire hard drive once a week on Friday. You decide to use the full backup method. Therefore, you perform a full backup every Friday. If the hard drive goes bad, you use the last backup to restore the hard drive.

You decide to back up the entire hard drive once a week on Friday. You decide to use the incremental method. Therefore, you perform a full backup on week

1. This shuts off all of the archive attributes, indicating that all of the files have been backed up. On week 2, week 3, and week 4, you perform incremental backups using different tapes or disks. Because the incremental backup turns the archive attribute, it backs up only new files and changed files. Therefore, all four backups make up the entire backup. It is much quicker to back up a drive using an incremental backup than a full backup. Of course, if the hard drive fails, you must restore backup #1, backup #2, backup #3, and backup # 4 to restore the entire hard drive.

After the backups are complete, you should check to see if the backups actually worked. You can do this by picking a nonessential file and restoring it to the hard drive. This helps discover if the backups are empty or a backup/restore device is faulty.

You should keep more than one backup. Tapes and disks do fail. One tech- nique is to rotate through three sets of backups. If you perform a full backup once a week, you would then use three sets of backup tapes or disks. During week 1, you use tape/disk #1. During week 2, you use tape/disk #2, and during week 3, you use tape/disk #3. On week 4, you start over and use tape/disk #1. If you have to restore a hard drive and the tape or disk fails, you can always go to the tape or disk from the week before. In addition, you should perform monthly backups and store then elsewhere. You might be surprised how many times a person loses a file but does not realize it for several weeks. If the data is important enough, you might consider keeping a backup set in a fireproof safe offsite. Lastly, when a system is initially installed and when you make any major changes to the system’s configuration, it is always recommended to make two backups before proceeding. This way, if anything goes wrong, you have the ability to restore everything to the way it was before the changes. The reason for the two backups is that tapes have been known to go bad on occasion.

CHAPTER 16: Backups and System Recovery

Some places use the Grandfather, Father, Son (GFS) backup rotation, which requires 21 tapes based on a five-day rotation. Each month, you create a grandfather backup, which is stored permanently offsite, never to be reused. Each week, you create a full weekly backup (father), and each day you create a differential or incremental backup (son).

After completing a backup, you should properly label the tape or disk before removing it and then store the tape and disk to a secure, safe place. In addi- tion, you should keep a log of what backups have been done The log keeps track of what was backed up and when it was backed up, which is especially useful if you need to rebuild the server. It also lets you know if someone is forgetting to do the backup.