Patent ID: 8255647

Claim:
A computer system comprising: a first computer; a second computer; a storage device; and a storage system, wherein the storage system includes: a first logical volume that is read from and written to by the first computer, and in which write data is written; a second logical volume that stores journal data that corresponds to data stored in the first logical volume with the journal data being delimited at predetermined points, and said second logical volume is unable to be read from and written to by the second computer; a third volume as a virtual volume; a virtual-volume creating unit that creates, when a backup instruction for the first volume at a predetermined point transmitted from the first computer is received, the third volume from which the second computer can read the journal data and in which the second computer can write the journal data; a mapping unit that maps an address where the journal data is stored in the second logical volume to the third volume created by the virtual-volume creating unit; and a backup unit that backs up the journal data by reading the journal data from the second logical volume through the third volume to which the address, where the journal data is stored in the second logical volume, is mapped by the mapping unit, and transferring the journal data to the storage device via the second computer in accordance with a read request to the third volume from the second computer.