According to one embodiment, a magnetic disk device comprising a magnetic disk, a magnetic head, and a controller that registers an address and a positioning error, determines whether or not a positioning error of a second sector that is two tracks ahead in a radial direction of a first sector to which a data is written is registered, and when the positioning error of the second sector is registered, sets a first threshold that allows a write operation for a positioning error of the first sector based on the positioning error of the second sector, and determines whether or not the positioning error of the first sector exceeds the first threshold, and stops the write operation when the positioning error of the first sector exceeds the first threshold.

A data storage device comprises a disk having a plurality of data tracks and a plurality of servo wedges wherein the plurality of servo wedges comprise a plurality of wedge repeatable runout (WRRO) fields configured to store a plurality of WRRO compensation values in connection with the plurality of data tracks. The data storage device may also include a read/write head configured to be actuated over the disk, and a controller configured to gather position error signal (PES) data needed for computation of the WRRO compensation values during a field operation of the data storage device. The data storage device may be further configured to adjust a position of the read/write head based on the WRRO compensation values.

Various illustrative aspects are directed to a data storage device comprising one or more disks; an actuator arm assembly comprising one or more actuator arms, and configured to position the one or more actuator arms over disk surfaces of the one or more disks; one or more fine actuators, disposed on the one or more actuator arms; and one or more processing devices. The one or more processing devices are configured to: output a driver current to the one or more fine actuators, wherein the one or more processing devices are configured to rate limit a rise of the driver current over time during an activation of the driver current to within a selected rate limit of current rise over time.

A system for determining a fly height includes a first head of a disk drive, a second head of the disk drive, a capacitive sensor circuit coupled to the first head and the second head, and a logic device coupled to the capacitive sensor circuit. The capacitive sensor circuit is configured to measure a first capacitance between the first head and the first disk, remove noise from the first capacitance using a second capacitance between the second head and the second disk, and based thereon determine a corrected first capacitance. The logic device is configured to determine the fly height between the first head and the first disk using the corrected first capacitance.

According to one embodiment, a magnetic disk device comprises a magnetic disk, a magnetic head, a monitoring unit, and a control unit. When carrying out write of data to a first track, if an absolute difference between a light output monitored by the monitoring unit at the time of write and a light output monitored last time by the monitoring unit exceeds a predetermined value, the control unit controls a position of a write head and writes data again to the first track or a second track one track before the first track.

A Data Storage Device (DSD) includes one or more magnetic disks with each magnetic disk including at least one recording surface. A segment mapping is generated having a predetermined number of segment entries per recording surface with each segment entry corresponding to a data segment of the recording surface. One or more segment entries include a first logical address corresponding to a first logical data block that begins in the corresponding data segment and at least one of the data segments is configured to store multiple logical data blocks. A target segment entry is located in the segment mapping corresponding to a highest logical address less than or equal to a requested logical address of a read command and a head of the DSD is moved to a beginning portion of a target data segment corresponding to the target segment entry to perform the read command.

Control circuitry is disclosed configured to control inner fine actuators of a first plurality of inner actuator arms and independently control a first outer fine actuator of a first outer actuator arm. Inner fine actuators of a second plurality of inner actuator arms are controlled while independently controlling a second outer fine actuator of a second outer actuator arm. Each actuator arm comprises at least one head configured to access a disk surface of a disk.

A data storage device is disclosed comprising a head actuated over a disk surface by an actuator arm. The actuator is controlled to press the actuator arm against a crash stop in order to write a plurality of bursts on the disk surface each with a different write parameter setting. Each burst is read in order to measure a quality metric for each burst, and an operating setting for the write parameter is configured based on the measured quality metrics.

According to one embodiment, a magnetic disk device includes a first disk, the second disk, and a first head which writes and reads to the first disk, a second head which writes and reads to the second disk, and a controller which calculates an estimated position at which the second head is estimated to be disposed on the second disk based on first relative position information related to a relative position in a radial direction between the first head and the second head when the first head is switched to the second head.

Control circuitry is disclosed configured to control inner fine actuators of a first plurality of inner actuator arms and independently control a first outer fine actuator of a first outer actuator arm. Inner fine actuators of a second plurality of inner actuator arms are controlled while independently controlling a second outer fine actuator of a second outer actuator arm. Each actuator arm comprises at least one head configured to access a disk surface of a disk.