In asynchronous remote copy, there is time difference between data update and remote copy in a primary storage system. The primary storage system loses data unreflected on a secondary storage system in disaster and cannot control the amount of data lost.The primary storage system obtains the data reflection state of remote copy between it and the secondary storage system to manage the amount of data update delay between the storage systems. When the amount of delay meets a configured start condition, a process of reducing the amount of delay is started. When the amount of delay meets a separately configured stop condition, the process of reducing the amount of delay is stopped. The configuration of whether the process of reducing the amount of delay is performed and the configuration of the conditions are performed from outside.