A method comprising: establishing a synchronous replication relationship comprising: creating, by a storage server, a base snapshot of a primary volume hosted by a first storage controller; performing a baseline transfer, using the base snapshot, of data from the primary volume to a second storage controller to create a secondary volume; until a synchronization criterion is met: creating an incremental snapshot of the primary volume; and performing an incremental transfer based upon the incremental snapshot and a prior snapshot of the primary volume; Further characterized by; initializing a dirty region log and using the dirty region log to track modifications of a file or logical unit number within the primary volume, the dirty region log comprising bits set to indicate whether regions of the file or LUN have been modified by client write requests; configuring a splitter object, for an endpoint, to split client write requests to the primary volume and to the secondary volume; responsive to the dirty region log tracking modifications, performing an asynchronous transfer from the primary volume to the secondary volume; initiating a synchronous transfer engine session between the primary volume and the secondary volume to process incoming client write requests, using the dirty region log, by: responsive to an incoming client write request corresponding to a dirty region, committing the incoming client write request to the primary volume; and responsive to the incoming client write request corresponding to a non-dirty region, committing the incoming client write request to the primary volume and committing a replication client write request, split from the incoming client write request, to the secondary volume; initiating a cutover scanner to scan the dirty region log for transferring data of dirty regions from the primary volume to the secondary volume; and responsive to the cutover scanner completing, designating the primary volume and the secondary volume as being in the synchronous replication relationship. creating, by a storage server, a base snapshot of a primary volume hosted by a first storage controller; performing a baseline transfer, using the base snapshot, of data from the primary volume to a second storage controller to create a secondary volume; until a synchronization criterion is met: creating an incremental snapshot of the primary volume; and performing an incremental transfer based upon the incremental snapshot and a prior snapshot of the primary volume; Further characterized by; creating an incremental snapshot of the primary volume; and performing an incremental transfer based upon the incremental snapshot and a prior snapshot of the primary volume; Further characterized by; initializing a dirty region log and using the dirty region log to track modifications of a file or logical unit number within the primary volume, the dirty region log comprising bits set to indicate whether regions of the file or LUN have been modified by client write requests; configuring a splitter object, for an endpoint, to split client write requests to the primary volume and to the secondary volume; responsive to the dirty region log tracking modifications, performing an asynchronous transfer from the primary volume to the secondary volume; initiating a synchronous transfer engine session between the primary volume and the secondary volume to process incoming client write requests, using the dirty region log, by: responsive to an incoming client write request corresponding to a dirty region, committing the incoming client write request to the primary volume; and responsive to the incoming client write request corresponding to a non-dirty region, committing the incoming client write request to the primary volume and committing a replication client write request, split from the incoming client write request, to the secondary volume; responsive to an incoming client write request corresponding to a dirty region, committing the incoming client write request to the primary volume; and responsive to the incoming client write request corresponding to a non-dirty region, committing the incoming client write request to the primary volume and committing a replication client write request, split from the incoming client write request, to the secondary volume; initiating a cutover scanner to scan the dirty region log for transferring data of dirty regions from the primary volume to the secondary volume; and responsive to the cutover scanner completing, designating the primary volume and the secondary volume as being in the synchronous replication relationship.