A data storage device includes a processor or hardware circuit. The processor or hardware circuit copies data stored in regions of a copy source volume to a copy destination volume. The processor or hardware circuit sets up in a memory a management table for the regions. The management table includes first information and second information. The first information indicates whether a bitmap has been set up. The bitmap represents a state of progress of the copy. The second information specifies a bit value to be used when setting up the bitmap. The processor or hardware circuit sets up in the memory the bitmap corresponding to the regions on the basis of the second information.