to host computers 503 and 504 to be used by a person of the network of working group 1 the network port 0 113 is connected to the network of working group 1 501 and the network port 1 113 is connected to the network of working group 2 502 the network of working group 2 502 is connected to host computers 505 and 506 to be used by a man of the network of working group 2 the administrator allocates logical disks 0 507 to 4 511 in the second storage system 101 the logical disk 0 507 and logical disk 1 508 are specified as a disk area 512 for the network of working group 1 they are both read and write enabled from the network of working group 1 the logical disk 2 509 and logical disk 3 510 are specified as a disk area 513 for the network of working group 2 they are both read and write enabled from the network of working group 2 a logical disk 4 512 is specified as a shared area 514 between the networks of working groups 1 and 2 that is it is read and write enabled from the networks of working groups 1 and 2 further the disk area 512 for the network of working group 1 is divided into an area 515 occupied by the network of working group 1 and an area 516 shared by the other network the area 515 occupied by the network of working group 1 is not recognized from the other network the area 516 shared by the other network is read only enabled from the other network.