Synthetic Full Backup - Frequently Asked Questions
Can I perform a synthetic full backup to one tape when the storage policy includes multiple clients?
No. The sequential-access nature of tape does not allow writing data onto its own source medium.
Clients A, B and C write to the same storage policy. Each has completed a full backup and several incremental backups. A synthetic full backup of client A must write to a new tape, since a source backup for client A exists on the current active destination tape. The new tape becomes the active tape for all clients.
Immediately after the synthetic full backup of client A, you run a synthetic full for client B. Client B has not performed any backups since client A's synthetic full, so it can write to the current active tape.
Next, you run an incremental backup of all clients. A new synthetic full backup of client C requires another new tape, since its last incremental backup is on the current active tape with client A and client B's synthetic full backups.