Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: maintain a refresh monitor for a refresh zone of one of the one or more disks, wherein the refresh zone comprises at least one data sector; update the refresh monitor in response to a write operation being performed in a track different than a track containing the refresh zone; update the refresh monitor at predefined time intervals based on a temperature of the one of the one or more disks or of the data storage device; and control a refresh operation of the refresh zone using the refresh monitor.

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: maintain a refresh monitor for a refresh zone of one of the one or more disks, wherein the refresh zone comprises at least one data sector; update the refresh monitor in response to a write operation being performed in a track different than a track containing the refresh zone; update the refresh monitor at predefined time intervals based on a temperature of the one of the one or more disks or of the data storage device; and control a refresh operation of the refresh zone using the refresh monitor.

According to one embodiment, a magnetic disk device includes a first write control section of writing first data and second data to each of the sectors of a predetermined track among the tracks, a second write control section of writing the first data to each of the sectors of a predetermined track among the tracks, and a selection control section of, when receiving a write command, estimating the time required from start of a process of the first write control section to end of the process, and selectively executing the process of the first write control section or a process of the second write control section by comparing the estimated time with a time limit specified in advance.

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: determine an initial track pitch based on a performance metric determined for the head; determine a track pitch adjustment based on a measure of servo pattern distortion associated with a region of the disk; and set a final track pitch for the region of the disk based on the track pitch adjustment and the initial track pitch.

Various illustrative aspects are directed to a data storage device, method, and one or more processing devices that are configured to: determine an initial track pitch based on a performance metric determined for the head; determine a track pitch adjustment based on a measure of servo pattern distortion associated with a region of the disk; and set a final track pitch for the region of the disk based on the track pitch adjustment and the initial track pitch.

Example control circuitry, data storage devices, and methods to use dual servo channels for burst gain switching are described. The data storage device may include two servo channels, such as the dual channels in a two-dimensional magnetic recording channel, that receive read signals for the same servo sector in parallel. One channel is calibrated to use a gain value for a first portion of the servo pattern, such as the preamble and Gray code for the servo address mark, and the other channel is calibrated to use a different gain value for a second portion of the servo pattern, such as the burst pattern. The resulting signal values may then be combined to determine the position error signal. Both channels may be configured to use different gain values for different portions of the read signal with corresponding gain switching and combining them may use the most reliable portions of each signal.

A controller of a magnetic disk device executes an integration operation each time a magnetic head passes through a servo sector during a write operation for a write target section of a first track among a plurality of tracks, so long as a positioning error amount in a servo sector that was most recently passed through by the magnetic head is within a range of an error threshold. The integration operation includes calculating an integrated offset amount by adding up positioning error amounts in two or more servo sectors including at least the servo sector that was most recently passed through by the magnetic head among all servo sectors that were passed through by the magnetic head during the write operation. The controller executes a protection operation for protecting data of a second track adjacent to the first track among the plurality of tracks based on the integrated offset amount.

Example control circuitry, data storage devices, and methods to use dual servo channels for burst gain switching are described. The data storage device may include two servo channels, such as the dual channels in a two-dimensional magnetic recording channel, that receive read signals for the same servo sector in parallel. One channel is calibrated to use a gain value for a first portion of the servo pattern, such as the preamble and Gray code for the servo address mark, and the other channel is calibrated to use a different gain value for a second portion of the servo pattern, such as the burst pattern. The resulting signal values may then be combined to determine the position error signal. Both channels may be configured to use different gain values for different portions of the read signal with corresponding gain switching and combining them may use the most reliable portions of each signal.

According to one embodiment of a magnetic disk device, a controller determines, by using a determination model, whether or not a distance in a radial direction from a target position related to a first track to a position of a magnetic head exceeds a threshold. The position of the magnetic head fluctuates from the target position toward a second track during execution of writing to the first track. The controller performs writing to the first track when the distance does not exceed the threshold, and performs no writing to the first track when the distance exceeds the threshold. The determination model is a learned model configured to receive pieces of position error information obtained by reading servo information from servo areas and output a value representing whether or not the distance exceeds the threshold while the magnetic head moves above the servo areas.