About the media servers for MSDP optimized duplication within the same domain
For optimized duplication within the same domain, the source storage and the destination storage must have at least one media server in common. The common server initiates, monitors, and verifies the duplication operation. The common server requires credentials for both the source storage and the destination storage. (For deduplication, the credentials are for the NetBackup Deduplication Engine, not for the host on which it runs.)
Which media server initiates the duplication operation determines if it is a push or a pull operation, as follows:
If the media server is co-located physically with the source storage server, it is push duplication.
If the media server is co-located physically with the destination storage server, it is a pull duplication.
Technically, no advantage exists with a push duplication or a pull duplication. However, the media server that initiates the duplication operation also becomes the write host for the new image copies.
A storage server or a load balancing server can be the common server. The common server must have the credentials and the connectivity for both the source storage and the destination storage.