Abstract: According to one embodiment, a magnetic disk device includes a disk, a head including a read head that reads data from the disk, a write head that writes data to the disk, and an assist element that generates energy to enhance write performance by the write head, and a controller that selects and performs a first recording mode and a second recording mode different from the first recording mode, and selects and performs one of the first recording mode and the second recording mode according to an assist effect of the assist element.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head including a read head that reads data from the disk, a write head that writes data to the disk, and an assist element that generates energy to enhance write performance by the write head, and a controller that selects and performs a first recording mode and a second recording mode different from the first recording mode, and selects and performs one of the first recording mode and the second recording mode according to an assist effect of the assist element.

Abstract: 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.

Abstract: 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.

Abstract: According to one embodiment, a magnetic disk device includes a disk having a first region in which a plurality of tracks is written and a second region that is positioned with a gap in a first direction of the radial direction of the first region, and in which a plurality of tracks is overwritten in the first direction, a head, and a controller that offsets part of a plurality of tracks which is overwritten in the second region in a second direction opposite the first direction to perform rewriting.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a normal recording region written in a normal recording and a shingled recording region written in a shingled recording, a head including a write head and a plurality of read heads, the head moving on the disk by rotation about a rotation axis, and a controller which selects and executes the normal recording and the shingled recording, wherein a first minimum value of a cross track interval in the radial direction of the disk between two read heads in the plurality of read heads in the normal recording region is smaller than a first maximum value of the cross track interval in the shingled recording region.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a normal recording region written in a normal recording and a shingled recording region written in a shingled recording, a head including a write head and a plurality of read heads, the head moving on the disk by rotation about, a rotation axis, and a controller which selects and executes the normal recording and the shingled recording, wherein a first minimum value of a cross track interval in the radial direction of the disk between two read heads in the plurality of read heads in the normal recording region is smaller than a first maximum value of the cross track interval in the shingled recording region.

Abstract: According to one embodiment, a magnetic disk device includes a disk having a first region in which a plurality of tracks is written and a second region that is positioned with a gap in a first direction of the radial direction of the first region, and in which a plurality of tracks is overwritten in the first direction, a head, and a controller that offsets part of a plurality of tracks which is overwritten in the second region in a second direction opposite the first direction to perform rewriting.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head including a main magnetic pole having a first end and a second end opposite to the first end in a radial direction of the disk, a write shield facing the main magnetic pole with a gap, and an assist element provided in the gap and at a position where a first distance between the first end and the assist element and a second distance between the second end and the assist element are different from each other, and a controller which controls a voltage applied to the assist element according to a shingled write direction in which a second track is overwritten on a first track.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including an assist part to assist recording of data into the magnetic disk, a controller configured to control the recording of data by the magnetic head based on a recording condition, and a memory configured to record a first threshold value used to define that an assist element included in the assist part is in a deterioration condition. Furthermore, the controller detects the condition of the assist element, determines whether or not the recording condition is changed based on the detected condition and the first threshold value stored in the memory, and changes the recording condition based on the result of the determination.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head including an assist part to assist recording of data into the magnetic disk, a controller configured to control the recording of data by the magnetic head based on a recording condition, and a memory configured to record a first threshold value used to define that an assist element included in the assist part is in a deterioration condition. Furthermore, the controller detects the condition of the assist element, determines whether or not the recording condition is changed based on the detected condition and the first threshold value stored in the memory, and changes the recording condition based on the result of the determination.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head including a main magnetic pole having a first end and a second end opposite to the first end in a radial direction of the disk, a write shield facing the main magnetic pole with a gap, and an assist element provided in the gap and at a position where a first distance between the first end and the assist element and a second distance between the second end and the assist element are different from each other, and a controller which controls a voltage applied to the assist element according to a shingled write direction in which a second track is overwritten on a first track.

Abstract: According one embodiment, a magnetic disk device includes a disk including a first region and a second region to which data before written to the first region is temporarily written, a head which writes data to the disk and reads data from the disk, and a controller which selectively performs conventional magnetic recording for writing a track at an interval in a radial direction of the disk and shingled magnetic recording for writing a track so as to overlap in the radial direction, and changes a cache data capacity of data which can be written to the second region in accordance with a first write capacity of data which can be written to the first region by the shingled magnetic recording.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head which writes data to the disk and reads data from the disk, and a controller which increases a first recording density of data to be written to a first sector having a first overwrite in the first sector and reduces a second recording density of data to be written to a second sector having a second overwrite different from the first overwrite, on a first track of the disk.

Abstract: In one embodiment, a magnetic disk device includes a disk with a recording surface, and a head. The recording surface includes a first area including a plurality of track groups in each of which data is recorded while a part of the data is overlappingly recorded, a second area provided separately in an outer circumference side from the first area, and including a plurality of track groups different from the first area in each of which data is recorded while a part of the data is overlappingly recorded, and a third area adjacent to the first area and the second area in a radial direction, and including a plurality of tracks which are arranged at a prescribed interval between the tracks.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head which writes data to the disk and reads data from the disk, and a controller which executes, in a first region segmented in a radial direction of the disk, at least one of conventional recording processing which writes a plurality of tracks with a space in between in the radial direction at a first linear recording density and shingled recording processing which writes a plurality of tracks on top of one another in the radial direction at a second linear recording density which is less than or equal to the first linear recording density.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head including a main magnetic pole having a first end and a second end opposite to the first end in a radial direction of the disk, a write shield facing the main magnetic pole with a gap, and an assist element provided in the gap and at a position where a first distance between the first end and the assist element and a second distance between the second end and the assist element are different from each other, and a controller which controls a voltage applied to the assist element according to a shingled write direction in which a second track is overwritten on a first track.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head which writes data to the disk and reads data from the disk, and a controller which executes, in a first region segmented in a radial direction of the disk, at least one of conventional recording processing which writes a plurality of tracks with a space in between in the radial direction at a first linear recording density and shingled recording processing which writes a plurality of tracks on top of one another in the radial direction at a second linear recording density which is less than or equal to the first linear recording density.

Abstract: According to one embodiment, a magnetic disk device includes a magnetic head, a magnetic disk on which a servo pattern used to position the magnetic head when data is to be recorded by means of the magnetic head is recorded, and a control section configured to set a recording condition for each predetermined unit of the magnetic disk on the basis of the servo pattern, and carry out recording of data on the magnetic disk according to the set recording condition.

Abstract: According to one embodiment, a magnetic disk device includes a disk, a head which writes data to the disk and reads data from the disk, and a controller which increases a first recording density of data to be written to a first sector having a first overwrite in the first sector and reduces a second recording density of data to be written to a second sector having a second overwrite different from the first overwrite, on a first track of the disk.