A controller provides a plurality of first sections with numerical information on a first scale. The plurality of first sections are obtained by dividing a recording surface of a magnetic disk in units of first memory areas in each of which a first volume of data can be written by an SMR method. The first scale corresponds to a sequence of the first sections. The controller provides a plurality of second sections with numerical information on a second scale. The plurality of second sections are obtained by dividing the recording surface of the magnetic disk in units of second memory areas in each of which the first volume of data can be written by a CMR method. The second scale corresponds to a sequence of the second sections. The controller executes a plurality of commands in order based on a numerical information on the first scale or the second scale.