Differential backups include all files that have changed since the last full or incremental backup. The difference between differential and incremental backups is that incremental backups include only the files that have changed since the last full or incremental backup.
Backup Exec provides two differential backup methods, one that uses archive bit and one that uses modified time to determine if the file was backed up. If you select to use the Full – Back up files – Using archive bit (reset archive bit) and want to run differential backups, you must use the Differential – Back up changed files since last full – Using archive bit (does not reset archive bit) method. If you select to use the Full – Back up files – Using modified time, you must use the Differential – Back up changed files since last full – Using modified time method.
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If you use modified time to determine if files have been backed up, the full and differential backups must use the same backup selection list. |
In most schemes, differential backups are recommended over incremental backups. Differential backups allow much easier restoration of an entire device than incremental backups since only two backups are required. Fewer required media also decreases the risk of not being able to restore important data because of media errors.
You should not mix differential and incremental backups together.
See About backup methods.