Abstract: According to one embodiment, a magnetic disk device includes: a magnetic disk having data spiral tracks extending from an outer circumference towards an inner circumference or from an inner circumference towards an outer circumference; a head configured to read data recorded in the data tracks of the magnetic disk that is rotating and to write data to the data tracks; and a controller configured to control the head to follow a predetermined data track in units obtained by subtracting a seek time required for the head to seek the predetermined data track from a rotation period.

Abstract: According to one embodiment, a disk drive includes an actuator, a servo controller, a calculation module and an adjustment module. The actuator is configured to move the head over a disk, in the radial direction of the disk. The servo controller is configured to make the head move along a target orbit on the disk, in accordance with the distance the actuator has been moved. The calculation module is configured to calculate, as disk runout, a virtual target orbit value supplied to the servo controller to suppress the disturbance at the target orbit. The adjustment module is configured to multiply the virtual target orbit value by a gain that has been preset.

Abstract: According to one embodiment, a disk drive includes an actuator, a servo controller, and a calculation module. The actuator is configured to move the head over a disk, in the radial direction of the disk. The servo controller is configured to make the head move along a target orbit on the disk, in accordance with the distance the actuator has been moved. The calculation module is configured to calculate, as disk runout, a virtual target orbit value supplied to the servo controller to suppress the disturbance at the target orbit.

Abstract: According to one embodiment, a disk drive is disclosed which has an offset measuring function for measuring a dynamic offset value necessary to a dynamic offset control using a DTM (discrete track media) type disk. A CPU (microprocessor) included in the disk drive writes offset measuring position information to an optimum position of lands on the disk and calculates a dynamic offset value based on the offset measuring position information.

Abstract: According to one embodiment, a disk drive has a disk, a CPU and a memory. The CPU measures servo intervals between the servo areas provided on the disk, and calculates changes of the servo intervals, which have resulted from a temperature change. The CPU detects a disk shift from the changes of the servo intervals. The CPU updates the disk-runout information stored in the memory, in accordance with the disk shift detected.

Abstract: According to one embodiment, a disk drive is disclosed which has an offset measuring function for measuring a dynamic offset value necessary to a dynamic offset control using a DTM type disk. A CPU included in the disk drive writes offset measuring position information to an optimum position of lands on the disk and calculates a dynamic offset value based on the offset measuring position information.

Abstract: According to one embodiment, a disk drive has a disk, a CPU and a memory. The CPU measures servo intervals between the servo areas provided on the disk, and calculates changes of the servo intervals, which have resulted from a temperature change. The CPU detects a disk shift from the changes of the servo intervals. The CPU updates the disk-runout information stored in the memory, in accordance with the disk shift detected.