Concurrent standard/high resolution logging of critical performance metrics and functional data for various functional areas including servo system, dataflow, channel, read/write, speed matching, and error recovery is achieved by segregating one or more rows of the tape map array for the purpose of logging only high resolution data. As performance data is logged to the standard resolution tape map by wrap and regional offset down tape, the reserved high resolution row logs data sequentially in the order it was processed on magnetic tape and not by its position on magnetic tape. The high-resolution performance data is concurrently logged with normal-resolution performance data as a supporting view with more detailed tape processing data should the normal-resolution performance data have inconclusive or insufficient content. High-resolution storage is structured for shorter regional logging or per-dataset logging of critical performance metrics and functional data, referred to herein as performance data.

According to one embodiment, a magnetic disk device includes a disk including a first region and a second region different from the first region, a head that writes data on the disk and reads data from the disk, an actuator that positions the head on the disk, and a controller which positions the head by driving the actuator and writes data in the first region and the second region with the head, a skew angle of the head with respect to a circumferential direction of the disk varying within a first angle in the first region, and varying, in the second region, from a second angle larger than the first angle to a third angle larger than the first angle and the second angle.

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.

A magnetic recording medium, includes a substrate; a magnetic layer; an underlayer between the substrate and the magnetic layer, the underlayer including a non-magnetic powder and a binding agent; and a back layer. In a case where w.sub.max and w.sub.min are respectively maximum and minimum of average values of width of the magnetic recording medium measured under four environments whose temperature and relative humidity are (10 C., 10%), (10 C., 80%), (29 C., 80%), and (45 C., 10%), respectively, w.sub.max and w.sub.min satisfy a relation of (w.sub.maxw.sub.min)/w.sub.min400 [ppm]. The substrate includes polyester. A squareness ratio in a vertical direction of the magnetic medium is 65% or more, and an average thickness of the magnetic recording medium is 5.6 m or less.

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. The head overlappingly records the data in the track groups of the first area in an order from the track locating at a center side to the track locating at the circumference side, and overlappingly records the data in the track groups of the second area in an order from the track locating at the circumference side to the track locating at the center side.

According to an embodiment, a magnetic disk device includes a magnetic disk including a first storage area and a second storage area different from the first storage area. In the second storage area, both of a first post code that is used to write user data in the first storage area by a first method and a second post code that is used to write user data in the first storage area by a second method are stored in advance. The first method is a method in which one track between two tracks adjacent to each other overlaps a part of the other track between the two tracks. The second method is a method in which two adjacent tracks do not overlap each other.

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.

According to one embodiment, a controller of a magnetic disk device determines whether or not to cause a magnetic flux control unit to generate a magnetic field, and in accordance with the determination result, causes a control circuit to apply a drive voltage to the magnetic flux control unit so that an assisted recording area and a non-assisted recording area are provided in a magnetic disk mixedly as desired.

A data storage device is disclosed comprising a head actuated over a disk. The head is used to read servo information from the disk and generate a position error signal (PES) representing a position of the head over the disk. A control signal is generated based on the PES and a triangle-shape dither signal, and the head is positioned over the disk using the control signal.

A data storage device includes a first data storage surface and a second data storage below the first data storage surface. The data storage device also includes a first micro-actuator coupled to a first arm that supports a first head over the first data storage surface, and a second micro-actuator coupled to a second arm that supports a second head over the second data storage surface. The data storage device further includes a coarse actuator, to which the first and second arms are coupled, that positions the first head and the second head between corresponding first and second tracks on the respective first and second data storage surfaces. Micro-actuator drive circuitry finely positions the first head over the first track and the second head over the second track by concurrently driving the first micro-actuator and the second micro-actuator in opposite directions.