Abstract: Proposed is technology for shortening the time required for analyzing and processing commands issued from multiple hosts and speeding up the processing. When a controller receives a command including random IO processing and the reception of commands is complete, it determines whether the valid extents prescribed in seek parameters attached to an LOC command overlap, and executes extent exclusive wait processing which causes access to the logical volume to enter a wait state or access processing to the logical volume based on the determination result. If the reception of commands is incomplete, the controller determines whether the access ranges (extents) designated in a DX command overlap, and executes extent exclusive wait processing or access processing to the logical volume based on the determination result.