Volume Replicator uses one of the SFW volumes as a circular log to store updates, and is called the Replicator Log. All updates to the data volumes in the Primary RVG are logged in the Replicator Log volume on the Primary host, before they are sent to the Secondary. Each update to the Primary RVG generates two update write requests; one to the Replicator Log volume and one to a data volume. Each RVG has one Replicator Log volume. Because the Replicator Log plays such an important role in maintaining the consistency of the data between the hosts it is very important to plan the size and layout of the Replicator Log appropriately. The maximum size of the Replicator Log can be derived from various criteria, however, the size of the Replicator Log volume should not be less than 110 MB.

The Secondary Replicator Log performs a different function from that of the Primary. Under normal operations, the Secondary Replicator Log volume is not used. It is used to maintain data consistency while Volume Replicator recovers from a temporary failure in communication between the Primary and Secondary, or from a Primary or Secondary host failure.