Synthetic Full Backup (Legacy Backup Format)
This article applies to the legacy backup format only. For information about synthetic full backup in the new backup format, refer to another article.
A synthetic full backup is a type of backup that creates a full backup using in-cloud data copying, significantly improving speed and efficiency by saving time and reducing network traffic. This method combines synthetic incremental backups with in-cloud data copying, where data is copied on the cloud side only, making it much faster than traditional full backups from an endpoint to the cloud. Synthetic full backup for legacy backup format is a combination of full and block-level backups.
With this option enabled, the first run of your backup plan will automatically force a full backup (synthetic backups will be executed during subsequent runs of this backup plan).
Enable synthetic full backup on the Advanced Options step of the legacy backup wizard. For some storage account this functionality may be unavailable.
Every time you edit a backup plan, the synthetic full backup conditions are re-evaluated. The synthetic full backup may be disabled if the changes you made affect compatibility (for instance, if you updated the storage account to a destination that doesn’t support synthetic full backups).