Backups and Archiving

Backing up data is essential to the survival and continuation of integral operations. Anyone in the support field who has spent an entire weeknight restoring a server can attest to this. Let’s cover a few of the basic backup schemes you’ll see in the wild.

Full Backup A full backup resets the archive bit of all files and backs them up accordingly.

Differential Backup This backs up all changed files since the last successful full backup. This job does not reset the archive bit. The reasoning behind not resetting the archive bit? Each differential is always based on the last full backup. Thus, any changes made since that last full backup are backed up…and backed up…and backed up. The benefit to this scheme is that during a full restore, only the last full backup and the most recent differential are needed to restore the entire site. The downside is that differentials can get huge!

Incremental Backup This job backs up all changed files since the last successful full backup, or since the last incremental. An incremental backup does reset the archive bit. What this equates to is a backup scheme that focuses on efficiency in the initial process. How? Once an incremental scheme has performed an incremental backup based on the last full, it bases all subsequent backups on the last incremental. In other words, you get a bunch of small backup jobs, all with the most recent changes. What this translates into is a tedious and lengthy full restoration job. The last full backup will need to be restored, as well as all the incrementals up to the current date.