Restoring from the full backup is a simple process because all files should be present on the full backup. However, if you are performing incremental backups, the process of restoring files changes.

Because an incremental backup backs up only some of the files, the process of restoring all the files is a follows:

  1. The last full backup must be restored.
  2. Every incremental backup must be restored that was done since the last full backup, in the order in which they were done.

This puts back all the files that were on the system when the full backup was done as well as every changed file since then. Any file that was changed more than once would be overwritten by a later restore of the file from later in the week. For example, if Monday’s incremental backup included files 2 and 5, the media would have the updated versions of these files. However, there may be updates to these files included in Wednesday’s incremental backup.

If any day is skipped by not restoring the incremental backup from that night, you may miss a file that is not backed up again. For example, by restoring all from every night’s incremental backup, except Thursday’s, you may not have the most up-to-date version of all files.

Therefore, when restoring from an incremental backup, you must restore the full backup and every incremental backup since the last full backup to the time of the system crash. This will allow you to completely recover all data or as close to it as possible.

Incremental restores require more time. Therefore, if your company wants the backups to take less time and the restores to take longer, an incremental backup is the backup strategy to use.

[tags]diana huggins,data protection,disaster planning & recovery,data loss,backup plan[/tags]