and secondary volumes is started in the consistency group forming a consistency group with a plurality of pairs such way is effective for a case in which data is to be stored in a plurality of storage volumes for example when write data is too large to be stored in one storage volume and when it is controlled so that one file data is stored in a plurality of storage volumes such assured synchronism of the pair state changes of volumes to the u201c split u201d in a consistency group is also effective for writing reading of data in from secondary volumes requested from the information processing apparatus 100 concretely if no consistency group is already formed data can be written read in from any paired secondary volume after the pair state is changed to the u201c split u201d while it is inhibited to write read data in from any secondary volume of which pair state is not changed to the u201c split u201d in this embodiment a batch split receiving flag id information of the consistency group management table 231 is used to assure the synchronism of such pair state changes of volumes to the u201c split u201d in the above consistency group next the processings for assuring such synchronism will be described with reference to the flowchart shown in fig6 the following processings are executed by the cpu 211 provided in the channel adapter 210 with use of the control program 214 program consisting of.