About synthetic backups

During a traditional full backup, all files are copied from the client to a master server or a media server. The files are copied even though those files may not have changed since the last incremental backup.

When NetBackup creates a synthetic full backup, NetBackup detects whether new or changed files have been copied to the media server during the last incremental backup. The client does not need to be running to combine the full backups and the incremental backups on the media server to form a new, full backup. The new, full synthetic backup is an accurate representation of the clients' file system at the time of the most recent full backup.

Because processing takes place on master and media servers instead of the client, synthetic backups help to reduce the network traffic. Files are transferred over the network only once. After the backup images are combined into a synthetic backup, the tapes or disk that contain the component images can be recycled or reclaimed. Synthetic backups can reduce the number of tapes or disk space in use.

Synthetic backups can be written to tape storage units or disk storage units, or a combination of both. If the backups use tape, the backups can be synthesized when drives are not generally in use. For example, if backups occur primarily at night, the drives can synthesize full backups during the day.

The Synthetic Backup option is available under the following conditions:

The policy type must be either Standard or MS-Windows.
The Collect True Image Restore Information With Move Detection option must be selected on the Policy Attributes tab.
The schedule that is created for a synthetic backup must have Synthetic Backup selected.
One of the following must be available:
- Disk storage unit(s) with adequate space available.
- Tape library(s) with multiple drives to read and write.
- A combination of disk storage unit(s) and tape library(s).