Patent ID: 7293193

Claim:
An array controller for controlling a disk array with redundancy, the disk array including a plurality of disk drives, the array controller comprising: a maximum address storage unit configured to store a maximum address, which is a maximum one of addresses of data-written areas of the disk drives; a data restoration unit configured to perform data restoration, wherein if one of the disk drives malfunctions and the disk array is rebuilt, the data restoration unit generates data corresponding to the malfunctioning disk drive based on data stored in first areas of remaining disk drives and arranges the generated data in a second area, which corresponds to the first areas and which is part of a new disk drive used in place of the malfunctioning disk drive, the first area being defined between a start address of the remaining disk drives to the maximum address stored in the maximum address storage unit; a write command execution unit configured to receive a write command, which includes an address indicating an area where data should be written, from a host that uses the disk array, and to execute the write command, the write command execution unit writing data designated by the write command in an area of at least one of the disk drives designated by the address included in the write command; a maximum address determination unit configured to determine whether an address indicating an area where data is written by the write command execution unit has exceeded the maximum address stored in the maximum address storage unit; and a maximum address update unit configured to update the maximum address to an address greater than the maximum address if the address indicating the area where the data is written by the write command execution unit has exceeded the maximum address stored in the maximum address storage unit.