In an asynchronous remote copy system, a primary site keeps a list of data blocks for which changes have been made to a primary file system and transmitted to a secondary file system at a secondary site. When the primary site becomes inoperative, the secondary site begins read/write access to the secondary file system and keeps a snapshot copy of the restart point. Once the primary site becomes operative, the primary file system is restored to the state of the secondary file system at the restart point by using the list of data blocks for obtaining from the snapshot copy the data of the blocks for which changes had been made to the primary file system after the restart point. Then the primary file system is synchronized to the secondary file system, and read/write access is switched back from the secondary file system to the primary file system.