Unitrends offers two flavors of replication: vaulting and cross-vaulting. Replication is simply the process of the electronic transfer of data from an on-premise location to an off-premise location. It's an alternative to rotational archiving that is more efficient because it takes human beings out of the process.

Vaulting refers to a one-way transfer of data from an on-premise to an off-premise location. Cross-vaulting refers to a two-way transfer. Regardless of whether vaulting or cross-vaulting is used, the fundamental premise is that data must be reduced as much as possible since typically there's a relatively low bandwidth WAN connection between premises. After some initial seeding process in which a copy of the initial backup is made from the on-premise appliance to the off-premise appliance, in-flight data deduplication begins occuring in order to optimize the WAN bandwidth.

The diagram below depicts the seeding and in-flight data deduplication process.