Patent ID: 7689611

Claim:
A computer system comprising: a host computer; and a storage system storing data accessed by said host computer; wherein said storage system includes a first physical storage area in one or more disks in said storage system and a controller for accessing the one or more disks in said storage system, wherein said first physical storage area corresponds to a first logical volume accessed by said host computer, wherein said host computer stores data in said first physical storage area, and stores a backup copy of the data at a certain point in time, wherein after said certain point in time, upon occurrence of a failure in a sequence of processing executed by said host computer, said host computer selects an unused second logical volume in said storage system, said second logical volume corresponding to a second physical storage area in said one or more disks, reads the backup copy of the data made at the certain point in time and writes the backup copy of the data to said second logical volume, wherein said host computer issues a swap request to said storage system, said swap request exchanging positional information of the first logical volume with that of the second logical volume, so that data of said first logical volume is interchanged with data of said second logical volume and said controller accesses said second physical storage area when said controller receives an access request to said first logical volume from said host computer, wherein said storage system sets a value of a device busy request of said positional information of each of said first logical volume and said second logical volume to indicate busy when said storage system receives said swap request from said host computer, and wherein said storage system issues a device busy request to said host computer, so as to keep consistency of said first logical volume and said second logical volume, when said storage system receives an access request to said first logical volume or said second logical volume from said host computer upon processing said swap request for said first logical volume and said second logical volume.