According to one embodiment, a magnetic disk device includes a disk including a first servo sector including a first preamble, a first servo mark, a first gray code, and first burst data, a head including a write head which writes data to the disk and a read head which reads data from the disk, and a controller which stops write processing, based on a write mask gate different from a first servo gate executing read processing of the first servo sector and a write gate executing the write processing to the disk.

According to one embodiment, a magnetic disk device including a disk, a head, and a controller configured to, when writing a first servo sector, a second servo sector, and a third servo sector in the order described according to a second route varying in a radial direction of the disk with respect to a first route, adjust first timing used to write the second servo sector next to the first servo sector, and adjust second timing used to write the third servo sector next to the second servo sector.

According to one embodiment, a magnetic disk device includes a disk including a recording region including a servo sector, a head configured to write data to the disk and read data from the disk, and a controller configured to acquire a plurality of correction data for a repeatable runout of the recording region, the correction data respectively corresponding to a plurality of measurement positions set based on a first linearity error acquired by reading the servo sector, and to correct a position of the head based on the correction data.

A data storage device is disclosed comprising a first head actuated over a first disk surface, and a second head actuated over a second disk surface. During a first revolution of the disk surfaces, a first set of servo sectors are written to the first disk surface and a second set of servo sectors are written to the second disk surface, wherein the first set of servo sectors are circumferentially offset from the second set of servo sectors. During a second revolution of the disk surfaces, at least one of the servo sectors in the first set is read from the first disk surface and at least one of the servo sectors in the second set is read from the second disk surface to control a position of the first head over the first disk surface.

According to one embodiment, a magnetic disk device includes a disk including two first servo sectors arranged side by side in a circumferential direction and a second servo sector located between the two first servo sectors, a head that writes data to the disk and reads data from the disk, and a controller that adjusts a second timing at which the second servo sector is demodulated based on a first timing at which the first servo sector is demodulated, and corrects a first initial phase of a first demodulation signal obtained by demodulating the second servo sector at the second timing, based on a first amplitude of the first demodulation signal.

According to one embodiment, a magnetic disk device includes a disk including a recording region including a servo sector, a head configured to write data to the disk and read data from the disk, and a controller configured to acquire a plurality of correction data for a repeatable runout of the recording region, the correction data respectively corresponding to a plurality of measurement positions set based on a first linearity error acquired by reading the servo sector, and to correct a position of the head based on the correction data.

A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks. A plurality of zones are defined for the disk, wherein each zone comprises a plurality of the data tracks. Position error signal (PES) repeatable runout (RRO) values are generated based on the servo data in a first zone, and data sector squeeze RRO values are generated based on data segments in the first zone. A first data track format for the first zone is generated based on the PES RRO values, and a second data track format is generated for the first zone based on the data sector squeeze RRO values.

According to one embodiment, a magnetic disk device includes a disk including a recording region including a servo sector, a head configured to write data to the disk and read data from the disk, and a controller configured to acquire a plurality of correction data for a repeatable runout of the recording region, the correction data respectively corresponding to a plurality of measurement positions set based on a first linearity error acquired by reading the servo sector, and to correct a position of the head based on the correction data.

Various illustrative aspects are directed to a data storage device comprising one or more disks, an actuator assembly comprising one or more disk heads; and one or more processing devices, configured to detect a plurality of areas with a coercivity lower than a threshold on the one or more disks; map out one or more sectors in each of the plurality of lower coercivity areas on the one or more disks; write data to, or read data from, the one or more disks, based at least in part on mapping out the one or more sectors in each of the plurality of lower coercivity areas. In some embodiments, the writing or reading data comprises writing data to, or reading data from, one or more sectors of the one or more disks that are not mapped out.

According to one embodiment, in a disk device, a controller adjusts a correction value of a radial position of servo track according to a ratio between amplitude of a correction value spectrum of a radial position of the servo track at a first circumferential position and at a second circumferential position when positioning control of the head to a target data track is performed on a basis of servo information read from the servo track. At the first circumferential position, a relative speed of a change in the radial position of the servo track with respect to a radial position of the target data track becomes a first speed. At the second circumferential position, a relative speed of a change in the radial position of the servo track with respect to the radial position of the target data track becomes a second speed.