Simple definition
A Synthetic Full Backup is a full backup rebuilt on the repository from an existing full backup and incremental restore points.
Technical definition
The backup software reads blocks already stored in the repository and composes a new full backup chain without reading the entire protected dataset again from the source machine.
What is it used for?
Create a periodic new full restore point while reducing network load and source-side read activity.
Practical example
A Veeam job can create a synthetic full during the weekend by combining the existing full and incremental backups stored in the repository.
Common issues
- The repository is too slow for synthetic operations
- Temporary space or repository capacity is insufficient
- Synthetic Full is confused with Active Full, which rereads data from the source
How it works / role
At the scheduled time, the backup engine identifies the required base full and incrementals and reads their blocks directly from the repository. It then creates a new consistent full backup on the backup storage, without rereading the entire protected dataset from production.
Related terms
Key takeaway: Exact behavior can vary by version, product, and architecture; always validate on the environment actually deployed.