Image Number 2 for United States Patent #6145067.
A disk array apparatus includes a plurality of physical disks forming a physical disk group which is logically divided into a plurality of unit areas. The unit areas are combined into a logical disk. This device includes a control section, a logical disk reconfiguration executing section, a P-EXTENT copying means, a read means, a write means, and a double write means. The control section controls an access to the logical disk in accordance with an external request. The logical disk reconfiguration executing section reconfigures the logical disk in accordance with an external request. The P-EXTENT copying means copies data from a unit area as a reconfiguration source to a unit area as a reconfiguration destination when the logical disk is reconfigured. The read means reads out data from a unit area. The write means writes data in a unit area that is not being reconfigured. The double write means writes data in both the unit area as the reconfiguration source and the unit area as the reconfiguration destination when the data is written in the unit area that is being reconfigured.