A mechanical linear actuator having a tubular member that is defined by a housing for rotatably and axially supporting a circular nut, a lead screw is mated to the circular nut so that it can move axially in and out of the tubular member. The method may also include determining whether a previous data transfer request has been indicated as combinable, and if it has been indicated as combinable, determining that a new data transfer request is addressed adjacent to the previous data transfer request. Each of the local data lines is associated with one of the memory areas and is connected to a two-wire master data line, common to all the memory areas, by a line circuit-breaker. Another head chip for recording and reproducing data in a state of being levitated from the recording surface of the disk and in a high recording density is provided in a position on the rear side of the second rail 26b with respect to the tangential direction R of the track.