Patent ID: 8065271

Claim:
A storage system, comprising: one or more disk storage devices; a tape storage device including a first tape storage medium and a second tape storage medium for storing data; and a controller, wherein the controller is configured to: control the one or more disk storage devices and the tape storage device; divide a storage area of the one or more disk storage devices for storing data into a plurality of volumes including a first volume, a second volume, and a third volume; include a memory location that stores a first bitmap indicating whether or not data stored in a storage region of the first volume is updated, a second bitmap indicating whether or not data stored in a storage region of the second volume is updated, a third bitmap indicating whether or not data stored in a storage region of the third volume corresponding to the first volume is updated, and a fourth bitmap indicating whether or not data stored in a storage region of the third volume corresponding to the second volume is updated; set a first copy pair between the first volume and the third volume; merge the first bitmap with the third bitmap; copy first data stored in the first volume to the third volume based on the merged first bitmap, wherein the first data is indicated by the first bitmap as being updated; read the first data from the third volume, and copy the first data to the first tape storage medium of the tape storage device; change the first copy pair to a second copy pair between the second volume and the third volume; merge the second bitmap with the fourth bitmap; copy second data stored in the second volume to the third volume based on the merged second bitmap, wherein the second data is indicated by the second bitmap as being updated; and read the second data from the third volume, and copy the second data to the second tape storage medium of the tape storage device.