Patent ID: 7401197

Claim:
A disk array system capable of mounting a plurality of disk drives, comprising: a memory arranged to store operation mode values, certificate data, and key data inherent to the disk array system; and a disk controller that controls data input/output to/from the disk drives; wherein each of the disk drives includes a disk medium and an HDD controller, the disk medium having a system area including an address X arranged to store data, and a data area arranged to store user data, the HDD controller controlling data input/output to/from the system area and the data area; wherein the disk controller is arranged to destage the certificate data to the system area, and to write the address of the destaged certificate data in the address X in the system area; wherein, upon a disk drive from among the disk drives being mounted in the disk array system, the disk controller determines whether the data stored in the address X is an address; if the data stored in the address X is determined not to be an address, the HDD controller compares the data stored in the address X with the key data stored in the memory, and if they do not correspond to each other, operates in an operation mode according to one of the operation mode values read from the memory, in which at least read access from the disk controller to the data area is prohibited; and if the data stored in the address X is determined to be an address, the HDD controller compares the certificate data stored at the address stored in the address X with the certificate data stored in the memory, and if they do not correspond to each other, operates in an operation mode according to one of the operation mode values read from the memory, in which at least read access from the disk controller to the data area is prohibited.