One way to avoid sending data over the network with your Vault job is to create multiple original backup images concurrently during your scheduled backup jobs. This avoids the need for your Vault session to do duplication. In this scenario, Vault needs to eject the backup tapes only. Vault takes no significant resource time, except for the Catalog Backup step. (Catalog Backup is necessary to capture the changed volume database information for each vaulted tape.)
Suppose you want the on-site copy of your backups to go to one robot, and the offsite copy to go to another robot. If you create multiple backup images concurrently, all destination storage units must be on the same media server. Therefore, your media server will need a storage unit on both robots (one storage unit for your on-site copy and one for the offsite copy).