1. A distribution processing unit of a shared storage, comprising: a master server for performing job management; a plurality of two or more slave nodes for executing independent jobs; a shared storage having a plurality of storage media for storing data; a management server for managing the shared storage; and a network connecting these components; wherein the shared storage includes a mapping means for dividing one or more LUs (Logical Units) composed of the plurality of storage media into two or more virtual sub LUs; and when a number of division of the virtual sub LUs is designated as a parameter for dividing the LUs, the mapping means rearranges the LUs into virtual sub LUs divided into the designated number, and the blocks within the LU are associated with the LU number of the virtual sub LUs and the blocks within the virtual sub LUs having the LU number.