A full synchronization is the copy of all data on the primary logical drive to the secondary logical drive. A full synchronization occurs when the Remote Mirror is created. A full synchronization also happens automatically after a link interruption or logical drive error that caused a Remote Mirror to become Unsynchronized is corrected.
The controller owner of the primary logical drive in the mirrored pair performs this operation in the background, while it is writing host I/O to the primary logical drive and sending associated remote writes to the secondary logical drive. You set a synchronization priority to determine how the controller owner of the primary logical drive will prioritize the full synchronization relative to the I/O activity.