The Backup Agent uses a technology called Intelliblox to only back up the changed parts of a file. This allows users to backup more files in the same backup window, since backups are smaller than they would be if the entire file was backed up each time. Backing up only the changes translates to file revisions using less data, allowing you to restore to more versions of a file without your usage growing to quickly.
With Exchange and SQL backups, after we have the initial full backup of the database, our Intelliblox technology is used to take block level changes of the database from one backup to another. The weekly full backups that run will be differential backups and contain block level changes. As a best practice, however, once that database changes over 50 percent we will back up a new full copy.
By default, Intelliblox is turned on as a feature within the software and is enabled globally across all backup sets. The functionality does not currently exist to have it turned off by default or to apply it to some backup sets but not others.
You can find Intelliblox settings within the Btab of the Backup Monitor under Security Settings. The default settings are to invoke Intelliblox if a file changes less than 50 percent and to not use Intelliblox if a file is under 64 KB in size. This setting is not available in the management portal.