Abstract: A method and disk apparatus, for writing data disk apparatus, that reduces the adverse influence of noise caused by data head writing on a read signal of a servo head even though the data head and the servo head are collaterally paired with no disks there between. A magnetic disk apparatus comprises a plurality of magnetic disks that are stacked at predetermined intervals; a servo head for reading servo signals recorded on a servo surface of one of the magnetic disks; a plurality of data heads, one of which is provided for each data surface of the magnetic disks with a first data head being collaterally positioned with the servo head, with no intervening magnetic disk, and second data heads being positioned at other than the collateral position; and an actuator for supporting the servo head and the data heads and for positioning the servo head and the data heads by moving them radially relative to the magnetic disks.

Abstract: Servo data to be stored on a servo disk in a magnetic recording apparatus for positioning a data head of the magnetic recording apparatus to a data disk of the magnetic recording apparatus, are formed in a train of four servo bytes arranged in accordance with four clock bits successively received. Each servo byte consists of a clock bit and a group of positional bits respectively, where the positional bit is set making a definite time space from the clock bit. The four definite time spaces of the corresponding positional bit in the four servo bytes make an arithmetic progression, in which the initial term is the definite time space of the positional bit in the first servo byte and the common difference is the time difference between two corresponding positional bits in two adjacent servo bytes. The time difference and a length of a gate pulse in which servo data signals are demodulated, are set, for example, to 20 ns and 160 ns, respectively.