Abstract: A disc array device for maintaining consistency of data. When write processing is interrupted and then restarted, new data may be stored in a nonvolatile memory and regeneration of parity may be impossible because data can not be read out normally from a disc device other than a disc device in which new data is to be written and a disk device for parity. In such a case, a special write executing unit overwrites the new data stored in the nonvolatile memory at a specified write position of the disk device in which new data is to be written.

Abstract: When write processing once interrupted is restarted, if new data is stored in a nonvolatile memory 34 and regeneration of parity is impossible because data can not be read out normally from a third disk device (for instance 32-2) other than a disk device (for instance 32-1) in which new data is to be written and a disk device (for instance 32-5) for parity, a data writing unit 113 in a special write executing unit 110 overwrites the new data stored in the nonvolatile memory 34 at a specified write position of an appropriate disk device (for instance 32-1).

Abstract: Each semiconductor memory module is divided into a plurality of access control units, and a service adapter copies the contents of the memory of the semiconductor memory module in which a memory error has occurred, to a spare semiconductor memory module one access control unit at a time. It is thus possible to evacuate the contents of the memory of the semiconductor memory module in which the memory error has occurred without stopping the semiconductor disk apparatus simply by adding the spare semiconductor disk apparatus. Since the copying operation is executed one access control unit at a time, a resource manager can conduct exclusive control also one access control unit at a time. A host apparatus therefore can access an access control unit portion which is not the object of copying even in the process of copying. In other words, the copying operation exerts no deleterious influence on the access of the host apparatus.