Abstract: A method of targeted corruption of user data in a shingled magnetic recording disk includes identifying user data on a Track_N targeted for corruption; identifying a readback centerline of the Track_N; identifying a readback centerline of an adjacent track to Track_N; acquiring user data of the adjacent track; and rewriting the user data of the adjacent track with an offset write centerline to overwrite magnetic material at the readback centerlines of both Track_N and the adjacent track.

Abstract: A method of targeted corruption of user data in a shingled magnetic recording disk includes identifying user data on a Track_N targeted for corruption; identifying a readback centerline of the Track_N; identifying a readback centerline of an adjacent track to Track_N; acquiring user data of the adjacent track; and rewriting the user data of the adjacent track with an offset write centerline to overwrite magnetic material at the readback centerlines of both Track_N and the adjacent track.

Abstract: A disk drive. The disk drive includes a head, a moving mechanism, a first peak filter, an adaptive peak filter, and a filter controller. The head is configured to read servo data on a disk at sampling frequency. The moving mechanism is configured to move the head in proximity with a recording surface of the disk. The first peak filter has a fixed peak frequency and a variable gain, and is configured to be inserted into a servo loop. The servo loop is configured to position the head with position error signals between servo data read by the head and a target position. The adaptive peak filter has a variable peak frequency and a variable gain, and is configured to be inserted into the servo loop. The filter controller is configured to control the gain of the adaptive peak filter according to the gain of the first peak filter.

Abstract: A disk drive. The disk drive includes a head, a moving mechanism, a first peak filter, an adaptive peak filter, and a filter controller. The head is configured to read servo data on a disk at sampling frequency. The moving mechanism is configured to move the head in proximity with a recording surface of the disk. The first peak filter has a fixed peak frequency and a variable gain, and is configured to be inserted into a servo loop. The servo loop is configured to position the head with position error signals between servo data read by the head and a target position. The adaptive peak filter has a variable peak frequency and a variable gain, and is configured to be inserted into the servo loop. The filter controller is configured to control the gain of the adaptive peak filter according to the gain of the first peak filter.

Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: Embodiments in accordance with the present invention provide a drive unit that is capable of satisfactorily performing the positioning control with disturbance components included in a position error signal being effectively controlled. According to one embodiment, an error signal generator of a drive unit generates a position error signal (PES) on the basis of servo data read out from a magnetic disk. On the assumption that a frequency of a periodic variation component included in the PES is a target frequency, if a target frequency deviates from an effective frequency range of a digital filter, a downsampler down-samples the PES, and then supplies the PES to the digital filter so that the effective frequency range is shifted. As a result, within the shifted effective frequency range, a setting changing unit can control a setting frequency of the digital filter so that the setting frequency follows the target frequency.

Abstract: Embodiments of the invention provide optimum servo patterns for perpendicular magnetic recording method. In one embodiment, a burst field of servo patterns is composed of burst-signal parts in each of which a constant frequency occurs successively and zero-signal parts each of which has been demagnetized to a state of zero-magnetization, and the total magnetization of the burst field is made approximately 0. The zero signal portions are formed by shutting off a write current at a time during an operation to record servo patterns on a disk initialized to a state of zero-magnetization. The total magnetization of all servo patterns is made approximately 0 by encoding an address mark field and a track code field of servo patterns by a phase shift method.

Abstract: Embodiments of the invention provide optimum servo patterns for perpendicular magnetic recording method. In one embodiment, a burst field of servo patterns is composed of burst-signal parts in each of which a constant frequency occurs successively and zero-signal parts each of which has been demagnetized to a state of zero-magnetization, and the total magnetization of the burst field is made approximately 0. The zero signal portions are formed by shutting off a write current at a time during an operation to record servo patterns on a disk initialized to a state of zero-magnetization. The total magnetization of all servo patterns is made approximately 0 by encoding an address mark field and a track code field of servo patterns by a phase shift method.

Abstract: An information recording/reproducing system in which a host system making access to a magnetic disk apparatus can be limited to a specific one. A magnetic disk apparatus includes an authentication key generating block for generating an authentication key on the basis of physical characteristic(s) of the magnetic disk apparatus itself. The magnetic disk apparatus and the host system have, respectively, authentication key recording block for recording the authentication key and authentication data generating block for generating authentication data on the basis of the authentication key. Access from the host system to information of the magnetic disk apparatus is controlled based on the authentication data of the host system and the authentication data of the magnetic disk apparatus.

Abstract: An information recording/reproducing system in which a host system making access to a magnetic disk apparatus can be limited to a specific one. A magnetic disk apparatus includes an authentication key generating block for generating an authentication key on the basis of physical characteristic(s) of the magnetic disk apparatus itself. The magnetic disk apparatus and the host system have, respectively, authentication key recording block for recording the authentication key and authentication data generating block for generating authentication data on the basis of the authentication key. Access from the host system to information of the magnetic disk apparatus is controlled based on the authentication data of the host system and the authentication data of the magnetic disk apparatus.

Abstract: An acceleration detecting apparatus for a magnetic disk apparatus capable of detecting with high reliability the disturbances such as rotational and translational shocks and vibrations applied externally to the magnetic disk apparatus to thereby prevent destruction or the like damages of data recorded on a disk of the magnetic disk apparatus upon occurrence of off-track event under the influence of the disturbance. The apparatus includes a pair of acceleration detectors for detecting acceleration in two directions extending discretely in parallel to each other. The acceleration detectors are disposed at positions closer to the magnetic disk relative to a pivot shaft for a head supporting arm as viewed in a longitudinal direction of an oblong box-like casing of the magnetic disk apparatus in a plane which forms an angle not greater than 10 degrees relative to the plane of the magnetic disk.