A magnetic disk device includes a plurality of tracks and a controller. The controller receives write data to be written to a first sector of a track, generates a first data string based on the write data and a logical identifier for the first sector, attempts to cause the first data string to be written to the first sector, determines whether a write error has occurred while the first data string is written to the first sector, generates a second data string based at least in part on the first data string, and in response to determining that no write error has occurred while the first data string is written to the first sector, writes a parity data string that is based at least in part on the second data string to a second sector of the track that stores parity data for the track.

According to one embodiment a magnetic disk device, includes a disk which includes a plurality of servo sectors radially extending in a radial direction and being discretely disposed with a gap in a circumferential direction, a head which writes data to the disk and reads data from the disk, and a controller which writes a plurality of pieces of correction data with respect to a repeatable run-out of the disk to a plurality of first sectors disposed between the servo sectors in a first region, and writes the pieces of correction data to a plurality of second sectors disposed between the servo sectors in a second region different from the first region.

A magnetic disk device according to one embodiment includes a magnetic disk on which multiple tracks are provided, a magnetic head, and a controller. At least one of the multiple tracks includes first sectors and a second sector. Each of the first sectors stores data segments. The second sector stores a parity for error correction. The magnetic head executes writing/reading to/from the magnetic disk. The controller executes processing of adjusting a guaranteed number of times by using a second sector being invalid. The guaranteed number of times indicates a number of times of writing for guaranteeing reading from an adjacent track.

According to one embodiment, a magnetic disk device includes a memory and a controller. The memory stores, for a predetermined track on a magnetic disk in the device, a counter, a counter threshold, and weights. The weights are individually set for divided areas of the predetermined track. The weights each have magnitude inversely proportional to a guaranteed number of times of data readout. When writing to an adjacent track of one or more of the divided areas is executed, the controller multiplies a number of times of writing by the weight corresponding to the one or more of the divided areas and adds the number of times of writing to the counter. When a numerical value of the counter reaches the counter threshold, the controller executes refresh to rewrite data in the predetermined track or executes reading for determining whether or not to perform the refresh.

According to the embodiment, an HDC receives a plurality of data segments from a host, and executes generation and addition of a first code and output of a data segment to which the first code is added to each data segment. An HDC calculates exclusive OR with respect to the first codes, and outputs obtained first information. The RWC performs data conversion and calculation of exclusive OR on the plurality of data segments to which the first code is added, and outputs the plurality of data segments after the data conversion and a track parity obtained by the calculation of the exclusive OR. The RWC acquires the first code from the plurality of data segments. The RWC calculates exclusive OR with respect to a group of the second codes which are the acquired first codes to acquire second information. The RWC compares the first information with the second information.

According to one embodiment, a hard disk drive includes a disk including a plurality of data areas, and a plurality of servo areas between the plurality of data areas, an arm holding a write head and a read arm, and a positioning module which positions the read head or the write head by rotating the arm, wherein the positioning module positioning the write head by positioning the read head, and adjusting a position of the read head or the write head, based on an output of the read head located in a data area between two servo areas adjacent in a peripheral direction, of the plurality of servo areas.

According to the embodiment, an HDC receives a plurality of data segments from a host, and executes generation and addition of a first code and output of a data segment to which the first code is added to each data segment. An HDC calculates exclusive OR with respect to the first codes, and outputs obtained first information. The RWC performs data conversion and calculation of exclusive OR on the plurality of data segments to which the first code is added, and outputs the plurality of data segments after the data conversion and a track parity obtained by the calculation of the exclusive OR. The RWC acquires the first code from the plurality of data segments. The RWC calculates exclusive OR with respect to a group of the second codes which are the acquired first codes to acquire second information. The RWC compares the first information with the second information.

According to one embodiment, a hard disk drive includes a disk including a plurality of data areas, and a plurality of servo areas between the plurality of data areas, an arm holding a write head and a read arm, and a positioning module which positions the read head or the write head by rotating the arm, wherein the positioning module positioning the write head by positioning the read head, and adjusting a position of the read head or the write head, based on an output of the read head located in a data area between two servo areas adjacent in a peripheral direction, of the plurality of servo areas.

A magnetic disk device according to an embodiment includes a disk including a plurality of tracks, a head configured to write and read data to and from the disk, and a controller configured to control an off-track of the head, which occurs when data is written to one track included in the plurality of tracks, within an allowable range of an amount of the off-track, which is set based on a count value of at least another track other than the one track.

A magnetic disk device according to an embodiment includes a disk including a plurality of tracks, a head configured to write and read data to and from the disk, and a controller configured to control an off-track of the head, which occurs when data is written to one track included in the plurality of tracks, within an allowable range of an amount of the off-track, which is set based on a count value of at least another track other than the one track.