A method for writing repeatable run-out data, representing a recurring contribution to position error, to a rotating constant-density magnetic storage medium, includes repeating, for each respective track at a respective radius of the constant-density magnetic storage medium, (1) determining a respective track pattern frequency based on track location and desired data density, (2) locating a position in a respective servo wedge on the respective track based on servo sync mark detection, (3) writing the repeatable run-out data to the respective servo wedge at a time delay, from the location of the position in the respective servo wedge, that is inversely proportional to the respective radius, to achieve a predetermined offset, and (4) repeating the determining, the locating and the writing for each servo wedge on the respective track of the constant-density magnetic storage medium.

A method for writing repeatable run-out data, representing a recurring contribution to position error, to a rotating constant-density magnetic storage medium, includes repeating, for each respective track at a respective radius of the constant-density magnetic storage medium, (1) determining a respective track pattern frequency based on track location and desired data density, (2) locating a position in a respective servo wedge on the respective track based on servo sync mark detection, (3) writing the repeatable run-out data to the respective servo wedge at a time delay, from the location of the position in the respective servo wedge, that is inversely proportional to the respective radius, to achieve a predetermined offset, and (4) repeating the determining, the locating and the writing for each servo wedge on the respective track of the constant-density magnetic storage medium.

According to one embodiment, a magnetic disk device includes a disk having a first sector including first servo data, first user data, and first correction information used to correct a data error, a head that writes data to the disk and that reads data from the disk, and a controller that changes, according to a first defect length of a defect generated in the first sector in a circumferential direction of the disk, a first sector length of the first sector in the circumferential direction.

According to one embodiment, a magnetic disk device includes a disk having a first sector including first servo data, first user data, and first correction information used to correct a data error, a head that writes data to the disk and that reads data from the disk, and a controller that changes, according to a first defect length of a defect generated in the first sector in a circumferential direction of the disk, a first sector length of the first sector in the circumferential direction.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including a read head to read data from the magnetic disk and a write head to write data to the magnetic disk, and a controller configured to control read/write from/to the magnetic disk by the magnetic head. The magnetic head includes a thermal actuator configured to project a head surface of the magnetic head to a recording surface of the magnetic disk, and a detector configured to detect a gap between the head surface and the recording surface of the magnetic disk. The controller controls a degree of projection of the magnetic head to the recording surface by the thermal actuator corresponding to the gap detected by the detector during the read/write.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including a read head to read data from the magnetic disk and a write head to write data to the magnetic disk, and a controller configured to control read/write from/to the magnetic disk by the magnetic head. The magnetic head includes a thermal actuator configured to project a head surface of the magnetic head to a recording surface of the magnetic disk, and a detector configured to detect a gap between the head surface and the recording surface of the magnetic disk. The controller controls a degree of projection of the magnetic head to the recording surface by the thermal actuator corresponding to the gap detected by the detector during the read/write.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including a read head to read data from the magnetic disk and a write head to write data to the magnetic disk, and a controller configured to control read/write from/to the magnetic disk by the magnetic head. The magnetic head includes a thermal actuator configured to project a head surface of the magnetic head to a recording surface of the magnetic disk, and a detector configured to detect a gap between the head surface and the recording surface of the magnetic disk. The controller controls a degree of projection of the magnetic head to the recording surface by the thermal actuator corresponding to the gap detected by the detector during the read/write.

According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including a read head to read data from the magnetic disk and a write head to write data to the magnetic disk, and a controller configured to control read/write from/to the magnetic disk by the magnetic head. The magnetic head includes a thermal actuator configured to project a head surface of the magnetic head to a recording surface of the magnetic disk, and a detector configured to detect a gap between the head surface and the recording surface of the magnetic disk. The controller controls a degree of projection of the magnetic head to the recording surface by the thermal actuator corresponding to the gap detected by the detector during the read/write.

A data storage device is disclosed comprising an actuator configured to actuate a head over a disk surface, and a vibration sensor configured to generate a vibration signal (VS). Control circuitry comprising a servo control system having a torque rejection curve (TRC) configured to control the actuator is configured to measure a position error signal (PES) of the head, and measure the VS output by the vibration sensor. A feed-forward compensator is configured based on PES/VS/TRC. While seeking the head across the disk surface, the VS is processed using the feed-forward compensator to generate a feed-forward compensation during a settle interval of the seek, and the actuator is controlled using the feed-forward compensation during the settle interval.

A data storage device is disclosed comprising an actuator configured to actuate a head over a disk surface, and a vibration sensor configured to generate a vibration signal (VS). Control circuitry comprising a servo control system having a torque rejection curve (TRC) configured to control the actuator is configured to measure a position error signal (PES) of the head, and measure the VS output by the vibration sensor. A feed-forward compensator is configured based on PES/VS/TRC. While seeking the head across the disk surface, the VS is processed using the feed-forward compensator to generate a feed-forward compensation during a settle interval of the seek, and the actuator is controlled using the feed-forward compensation during the settle interval.