Patent ID: 7089386

Claim:
A storage system, comprising: a plurality of disk drives located in a disk array system; and a controller located in said disk array system and coupled to an information processing device and for transferring data sent from said information processing device to a plurality of first logical volumes relating to said disk drives and for controlling a first group having both said first logical volumes and a plurality of second logical volumes, said second logical volumes being backup volumes of said first logical volumes and being used to maintain consistency among data stored in said second logical volumes; wherein said controller processes to receive a command sent to said first group, start, in accordance with said command, to change from a first status to a second status in which a relationship between said first logical volumes and said second logical volumes is split, receive a write command sent from said information processing device to a first logical volume of said first logical volumes during said period of changing to said second status, and if said write command is sent to the first logical volume in the first group relating to the command, during the period of changing to the second status, pause momentarily writing of data of said write command, and write data related to said write command to said first logical volume after changing of the relationship between said first logical volumes and said second logical volumes to said second status; and if said write command is sent to another group to which the command is not related, during the period of changing to the second status, write data of the write command to one of logical volumes in said another group.