Abstract: Conventionally, it has been impossible to choose storage subsystems for selective implementation of I/O delay to prevent buffer from overflowing during remote copy. According to this invention, in a management computer that manages serially connected plural storage subsystems in a computer system, the computer system having a host computer to write data in the storage subsystems, the plural storage subsystems each have one or more logical volumes where data is stored and a buffer where data is stored temporarily, the logical volume of one of the storage subsystems and the logical volume of another of the storage subsystems form a pair for remote copy, and the management computer observes the usage of each buffer and issues, when the usage of the buffer exceeds a given threshold in a first storage subsystem, a command to delay executing write processing to the storage subsystems that are upstream of the first storage subsystem.