Abstract: An apparatus may include a first and second servo channels configured to output first and second position information to first and second writers, respectively, via a shared write path such that the first and second writers write first and second position information to first and second magnetic recording medium surfaces, respectively. In addition, the apparatus may include a controller configured to control the shared write path such that write access is changed between the first servo channel and second servo channel a plurality of times during a revolution of the first magnetic recording medium surface and second magnetic recording medium surface.

Abstract: Method and apparatus for predicting data storage device failures using adaptive failure prediction modeling. In some embodiments, monitored parameters are used to predict a potential imminent failure of a first data storage device using a first copy of a first failure prediction model (FPM). Data associated with the predicted potential imminent failure are transferred by the device across a computer network to a host device. The host device generates an updated, second FPM responsive to the transferred data as well as from data from at least a second data storage device transmitted across the computer network having a second copy of the first FPM. A first copy of the updated, second FPM is transferred, via the network, for use by the second data storage device.

Abstract: A tape transport control system with enhanced regulation of tape tension and velocity over the entire length of the tape. For example, a closed-loop control system for controlling a tape transport includes circuitry adapted to output a signal representing a tape velocity at a tape head, circuitry adapted to output a signal representing a tape velocity at the first tape reel and a signal representing a tape velocity at the second tape reel, circuitry adapted to output a signal representing a tape tension, and circuitry adapted to, based on the received signals, generate control signals to control the tape velocity at least at one of the tape head, the first tape reel, the second tape reel, and the tension of the tape, using controller gains that depend on a longitudinal position of the tape, and to implement a system transfer function that is approximately independent of the longitudinal position.

Abstract: A plurality of commands is received from a host to perform at least one of reading data and writing data on a magnetic storage media of a Data Storage Device (DSD). The plurality of commands is clustered for performance based at least in part on a timing control of a fly-height heater of the DSD that is configured to adjust a flying height of a head of the DSD while the head is flying over the magnetic storage media. A cluster of commands is performed including the plurality of commands by controlling the head to perform at least one of reading and writing data on the magnetic storage media for the cluster of commands.

Abstract: A magnetic recording apparatus includes a magnetic recording medium; a magnetic recording head including a first magnetic pole part, a second magnetic pole part, and a magnetic flux control part provided between the first magnetic pole part and the second magnetic pole part, wherein the magnetic flux control part includes a first layer provided between the first magnetic pole part and the second magnetic pole part, a second layer provided between the first magnetic pole part and the first layer, and a third layer provided between the second magnetic pole part and the first layer; an electrode for applying a current to the magnetic flux control part; and an electric circuit for energizing the current to the electrode, wherein an oscillation frequency of magnetization of the magnetic layer is greater than a ferromagnetic resonance frequency of the magnetic recording medium.

Abstract: A disk device includes first and second recording surfaces, a first head for the first recording surface, including a first heater which generates heat via a first electric power, a second head for the second recording surface, including a second heater which generates heat via a second electric power, and a control circuit configured to execute a first preheating operation in which the first electric power is supplied to the first heater for a first time interval prior to starting a first writing process to write data on the first recording surface by the first head, and to execute a second preheating operation in which the second electric power is supplied to the second heater for a second time interval prior to starting a second writing process to write data on the second recording surface by the second head. The first time interval is different from the second time interval.

Abstract: Systems and techniques for communicating data as a function of frequency are presented. In an implementation, a system includes a microelectromechanical systems (MEMS) sensor, a digital signal processor and a frequency detection circuit. The digital signal processor is coupled to the MEMS sensor. The frequency detection circuit receives data encoded as a function of frequency from the digital signal processor via a clock communication channel.

Abstract: A magnetic disk device includes a disk, a head configured to write data on the disk, and a controller. The controller generates a target trajectory of the head in a circumferential direction for writing to a plurality of sectors in a current track, wherein the target trajectory is based on an actual trajectory of the head for writing to a plurality of sectors in a previously written track that is adjacent to the current track, determines that the previously written track is discontinuous between an initial sector of the previously written track and an end sector of the previously written track by a radial offset, generates a corrected trajectory for writing the plurality of sectors in the current track, and controls a position of the head in a radial direction based on the corrected trajectory while writing to the plurality of sectors in the current track.

Abstract: The magnetic tape device includes a magnetic tape including a magnetic layer, in which an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical direction squareness ratio of the magnetic tape is 0.65 to 1.00, Ra measured regarding a surface of the magnetic layer is equal to or smaller than 2.0 nm, and a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is 45 to 65 atom %.

Abstract: The magnetic tape device includes a magnetic tape including a magnetic layer, in which an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical direction squareness ratio of the magnetic tape is 0.65 to 1.00, Ra measured regarding a surface of the magnetic layer is equal to or smaller than 2.0 nm, and a C—H derived C concentration calculated from a C—H peak area ratio of C1s spectra obtained by X-ray photoelectron spectroscopic analysis performed on the surface of the magnetic layer at a photoelectron take-off angle of 10 degrees is 45 to 65 atom %.

Abstract: A microactuator for a suspension is described. The microactuator includes a multi-layer PZT device having a first face and an opposite second face. Each layer of the multi-layer PZT device is configured to operate in its d15 mode when actuated by an actuation voltage. The layers are configured as a stack such that each layer is configured to act in the same direction when actuated such that the first face moves in shear relative to the second face.

Abstract: A servo control device according to the present invention includes a speed command generation unit, a torque command generation unit, a speed detection unit, a speed control loop, a speed control gain setting unit for setting a speed control gain for the speed control loop, a sinusoidal disturbance input unit for performing a sinusoidal sweep on the speed control loop, a frequency characteristic calculation unit, and a gain adjustment unit. When the speed control loop has fallen into an oscillation state and has become unstable owing to the increased speed control gain, the speed control gain is reduced and the sinusoidal sweep is temporarily stopped. After the speed control loop is stabilized using the speed control gain which is lower than in the unstable state, the sinusoidal sweep is restarted.

Abstract: During in-drive writing of a servo spiral on a disk surface, a servo spiral can be distinguished during demodulation from adjacent servo spirals on the same disk surface. When a set of servo spirals is written on a disk surface, a first spiral is written to include a first identifying characteristic and the following spiral is written to include a second identifying characteristic. The identifying characteristic may include embedded sync marks encoding a certain numerical value, a unique frequency of high-low transitions included in each spiral, and/or a unique frame size.

Abstract: A hard disk drive (HDD) is configured to move a read head over a region of a storage surface that includes unreadable segments of reference spirals that have been overwritten by a reference spiral in a set of spirals that is currently being written on the storage surface. By moving the read head across the region of the storage surface at a return radial velocity that is selected such that the write head crosses no consecutive reference spirals at an unreadable segment, the servo system of the HDD does not experience an error due to crossing multiple consecutive reference spirals at unreadable segments. Thus, a set of spirals that includes partially damaged reference spirals can be employed to control the position of a read head. Consequently, a second surface is not required for the set of spirals employed in controlling the writing process.

Abstract: A PZT microactuator such as for a hard disk drive has a restraining layer bonded on its side that is opposite the side on which the PZT is mounted. The restraining layer comprises a stiff and resilient material such as stainless steel. The restraining layer can cover most or all of the top of the PZT, with an electrical connection being made to the PZT where it is not covered by the restraining layer. The restraining layer reduces bending of the PZT as mounted and hence increases effective stroke length, or reverses the sign of the bending which increases the effective stroke length of the PZT even further. The restraining layer can be one or more active layers of PZT material that act in the opposite direction as the main PZT layer. The restraining layer(s) may be thinner than the main PZT layer.

Abstract: Various embodiments for error recovery in a data storage environment, by a processor device, are provided. For monitoring signal from one or more read channels in a tape storage drive, a variable range of offsets organized by row into a table is selected by a microcode algorithm and applied by a track following servo mechanism of the tape storage drive to position a read head in relation to a track of a tape media at an offset up to and including beyond a predetermined margin of the track.

Abstract: A control device is provided which can perform a retraction operation of a head included in a disk storage device with lower power consumption. The control device of the disk storage device includes a control unit that controls a motor and retracts the head from over a disk to a ramp mechanism when power supply is shut down, an acquisition unit that acquires information related to a moving distance of the head that retracts to the ramp mechanism, and a calculation unit that calculates the moving distance of the head based on the information acquired by the acquisition unit. The control unit switches an operation of the motor from a first retract operation to a second retract operation when determining that the head reaches a first position after passing through an inclined surface of the ramp mechanism based on the moving distance calculated by the calculation unit.

Abstract: Gain values used by a variable gain amplifier (VGA) to read servo marks of a heat-assisted recording medium are measured. Sector-specific, repeatable gain values that indicate an expected VGA gain at a desired clearance are determined based on the measured gain values. The sector-specific, repeatable gain values are used as input to a closed-loop clearance controller together with measured values of servo VGA gain while writing data to the recording medium.

Abstract: The presently disclosed technology teaches integrating disc drive electronics into a transducer head. Decreased electrical transit times and data processing times can be achieved by placing the electronics on or within the transducer head because electrical connections may be made physically shorter than in conventional systems. The electronics may include one or more of a control system circuit, a write driver, and/or a data buffer. The control system circuit generates a modified clock signal that has a fixed relation to phase and frequency of a bit-detected reference signal that corresponds to positions of patterned bits on the disc. The write driver writes outgoing data bits received from an external connection to off-head electronics directly to the writer synchronized with the modified clock signal. The data buffer stores and converts digital data bits sent from the off-head electronics to an analog signal that is synchronized with the modified clock signal.

Abstract: Apparatus and method contemplating an in-situ test method for a head gimbal assembly (HGA). The method includes individually exciting a pair of opposing-effect microactuators supporting the read/write head adjacent a data storage media; summing the outputs from the microactuators to derive a spectral frequency response of the HGA; determining a resonant frequency from the spectral frequency response; driving the microactuators at the resonant frequency; and varying the read/write fly height apart from the data storage media to correlate contact with a maximum response of the microactuators.

Abstract: According to one embodiment, a magnetic disk apparatus includes a magnetic head, a voice coil motor, a driving circuit, and a VCM resistance estimation unit. The magnetic head accesses a magnetic disk. The voice coil motor drives the magnetic head over the magnetic disk. The driving circuit applies a VCM current to the voice coil motor. The VCM resistance estimation unit estimates a VCM resistance in the voice coil motor based on the saturated VCM current and a velocity of the magnetic head.

Abstract: A method, apparatus, and system are provided for implementing track following using signal asymmetry metrics monitored during read back in hard disk drives (HDDs). Signal asymmetry metrics monitored during read back are used together with a position error signal (PES) to correct and guide the position of a read sensor with respect to a written track in the HDD.

Abstract: An apparatus comprising a slider and a detector coupled to the slider. The slider is configured for writing data to and reading data from a magnetic recording medium. The slider comprises a heater configured to receive a modulated signal and cause oscillation in a spacing between the slider and the medium. At least one heat generating component of the slider is configured to receive a modulated signal. A contact sensor is situated on the slider to receive heat generated by the at least one heat generating component. The detector is configured to measure a response signal of the heated contact sensor as the slider approaches the medium. The detector is further configured to detect contact between the slider and the medium in response to the response signal reaching a predetermined threshold.

Abstract: An apparatus comprises a slider configured for heat-assisted magnetic coupled to a controller. The slider comprises a writer, a heater, a near-field transducer, and an optical waveguide for communicating light from a laser diode to the near-field transducer. The controller is configured to set a target pre-write clearance of the slider prior to performing a write operation, set a target write clearance of the slider for performing the write operation, and determine a difference between the target pre-write and write clearances to define a target pre-write clearance offset. The controller is also configured to measure, for a plurality of different target pre-write clearance offsets, a writability metric for the slider while sweeping a laser diode current, and adjust the target pre-write clearance offset so that the writability metric reaches a predetermined threshold. The controller is further configured to perform subsequent write operations using the adjusted target pre-write clearance offset.

Abstract: A magnetic disk device includes a magnetic disk having a plurality of tracks, a magnetic head used for writing data on the magnetic disk and reading data from the magnetic disk, a controller configured to control seek operations of the magnetic head, and a vibration sensor. The controller predicts a first vibration caused by a currently executed seek operation, based on a seek control signal, predicts a second vibration based on vibration detected by the sensor, and determines an adjusted start time of the currently executed seek operation so that a phase of the first vibration does not match a phase of the second vibration.

Abstract: According to one embodiment, a VCM resistance estimation unit estimates a VCM resistance in a voice coil motor based on an acceleration and a velocity of a magnetic head with a VCM voltage saturated, and an equivalent current force constant estimation unit estimates an equivalent current force constant of the voice coil motor based on the acceleration and the velocity of the magnetic head with the VCM voltage saturated.

Abstract: A method of writing servo spirals for spiral-based self-servo writing includes determining control parameters for controlling movement of a write head between a first and a second disk radial location at a first velocity, writing a first spiral while controlling the movement of the write head between the first and the second disk radial location at the first velocity according to the determined control parameters, writing a second spiral while controlling movement of the write head between the first and the second disk radial location at a second velocity that is different from the first velocity, based on timing and location information from the first spiral, and writing a third spiral while controlling movement of the write head between the first and the second disk radial location at the first velocity according to the determined control parameters and based on timing and location information from the second spiral.

Abstract: An apparatus for driving a voice coil actuator of a camera and a method thereof are provided. The driving apparatus performs input shaping based on a resonance frequency of a voice coil actuator and damping of vibration in the voice coil actuator to generate a control signal using a shaping signal as an initial input from an unshaped control signal, and thereby drives the voice coil actuator using the control signal subjected to input shaping. The shaping signal is provided to remove the resonance of the voice coil actuator, and may be a pure shaping signal, such as a multi-step shaping signal or a toggle shaping signal, or a convoluted shaping signal obtained by convoluting such pure shaping signals. The driving apparatus may significantly reduce residual vibration and may enhance an auto-focus function of the voice actuator using input shaping control based on damping.

Abstract: A read/write head has a set of components that at least include: at least one clearance actuator; at least one read transducer configured to read from a magnetic recording medium; and at least one write transducer configured to write to the magnetic recording medium. A switch network is coupled to the set of components and configured to, in response to a control signal, couple a selected sub-combination of the components to a common set of signal lines. The coupling of the selected sub-combination facilitates operation in a selected mode of the read/write head.

Abstract: A driver device coupled to a winding of an electro-mechanical actuator includes: a power stage driving the winding in a discontinuous mode by alternating conduction on-phases to off-phases, and a sensor circuit sensing a voltage across the winding in an off-phase, wherein, during such an off-phase the voltage across the winding includes a residual voltage which decays to zero. The power stage drives the winding from an on-phase to an off-phase by applying to the winding a reverse current pulse to invert the direction of flow of the current through the winding and produce an oscillation of the residual voltage, whereby the residual voltage includes a zero-crossing point after the current through the winding is exhausted. The sensor circuit senses the voltage across the winding at this zero-crossing point, whereby the voltage sensed across the winding at the zero-crossing point is indicative of the back electromotive force of the winding.

Abstract: A data storage device is disclosed comprising a first disk surface comprising a plurality of servo tracks, a first head actuated over the first disk surface, wherein the first head comprises a first read element, and a second read element. During a write operation first servo data in a first servo track is read using the first read element to generate a first read signal, and the first head is servoed over the first servo track based on the first read signal while writing data to the first disk surface. Second servo data is read using the second read element to generate a second read signal, and the write operation is aborted when the first read signal indicates a shock event is affecting the servoing of the first head and the second read signal confirms the shock event.

Abstract: Provided herein is a method, including creating a first pattern in a data region of a substrate, and creating a second pattern in a servo region of a substrate. A circumferential line pattern is created overlapping the first pattern to create rectangle-shaped protrusions in the data region of the substrate. A chevron pattern is created overlapping the second pattern to create chevron-derived protrusions in the servo region of the substrate.

Abstract: A perpendicular magnetic recording medium according to an embodiment includes a substrate and perpendicular magnetic recording layer. The perpendicular magnetic recording layer includes a recording portion and non-recording portion. The recording portion has patterns regularly arranged in the longitudinal direction, and includes magnetic layers containing Fe or Co and Pt as main components, and at least one additive component selected from Ti, Si, Al, and W. The non-recording portion includes oxide layers formed by oxidizing the side surfaces of the magnetic layers, and nonmagnetic layers formed between the oxide layers.

Abstract: The invention generally relates to a hard disk drive with a disk, a read/write head, a z-axis actuator, and a controller. A surface of the disk and/or the head can be bare and thus devoid of any overcoat or lubricant layer, or alternatively the disk surface can have one or more layers with a combined thickness of less than 4 nanometers and the head can have a layer with a thickness of less than 2 nanometers. The hard disk drive can be enclosed, and its enclosed space can be a low pressure environment such as a near-zero or a zero pressure environment.

Abstract: A slider having an air bearing surface is configured for heat-assisted magnetic recording. A writer of the slider comprises a writer coil. A current source is configured to supply a modulated writer current at a first predetermined frequency to the writer coil. A writer heater is situated proximate the writer and configured to thermally actuate a writer region of the air bearing surface. A contact sensor is situated proximate the writer coil and configured to sense temperature changes indicative of changes in spacing and contact between the slider and a magnetic recording medium. A signal produced by the contact sensor oscillates at the first predetermined frequency. A detector is coupled to the contact sensor. The detector is configured to detect contact between the thermally actuated writer region and the medium using the contact sensor signal.

Abstract: A change in servo active gain control values is determined from a beginning of a writing of a test region of a recording medium to an end of the writing of the test region. The servo active gain control values are read from servo marks by a read transducer of a read/write head during the writing. After writing of the test region, the test region is read by the read transducer to determine a change in recorded amplitude from the beginning of the writing to the end of the writing. A gamma value of the read/write head is determined based on the change in servo active gain control values and the change in recorded amplitude.

Abstract: An adjusting method for a magnetic disk device including a disk, a head that writes data on the disk, a controller circuit that outputs write data and a control signal related to the write data, and an integrated circuit that outputs a write current to the head, includes adding a delay to a timing of polarity inversion of one bit of the write data or the control signal, outputting the write data and the control signal added with the delay from the controller circuit to the integrated circuit, outputting from the integrated circuit to the head, the write current having a current value that is changed at one of timings of polarity inversion of the write data, according to the control signal, and adjusting a deviation between the write data and the control signal, based on the output write current.

Abstract: Systems and methods for partial bad block reuse may be provided. Data may be copied from a block of a first memory to a block of a second memory. A post write read error may be detected in a first portion the data copied to the block of the second memory without detection of a post write read error in a second portion of the data copied to the block of the second memory. The block of the second memory may be determined to be a partial bad block usable for storage in response to detection of the post write read error in the first portion of the data but not in the second portion of the data.

Abstract: A server disk drive holder assembly includes an outer tray, an inner tray and a latch arm. The outer tray includes a locking hole. The inner tray overlaps on the outer tray. The inner tray is movable with respect to the outer tray. The inner tray includes a fastening hole. A latch arm is pivotally disposed on an outer side of the outer tray. The latch arm includes a hook portion. When the locking hole is aligned with the fastening hole, the hook portion is inserted through the locking hole to be engaged with the fastening hole. A disk drive can be clamped between the outer tray and the inner tray. By utilizing the movable latch arm to fasten the outer tray and the inner tray, the disk drive can be quickly mounted and dismounted.

Abstract: Methods and apparatuses for optimizing the performance of a storage system comprise a FLASH storage system, a hard drive storage system, and a storage controller. The storage controller is adapted to receive READ and WRITE requests from an external host, and is coupled to the FLASH storage system and the hard drive storage system. The storage controller receives a WRITE request from an external host containing data and an address, forwards the received WRITE request to the FLASH storage system and associates the address provided in the WRITE request with a selected alternative address, and provides an alternative WRITE request, including the selected alternative address and the data received in the WRITE request, to the hard drive storage system, wherein the alternative address is selected to promote sequential WRITE operations within the hard drive storage system.

Abstract: Using a high sample rate dPES, together with pulsed heater and lock-in technique, to improve dPES SNR for contact detection between the head and media surface. Steps of powering a transducing head actuator with pulsed input signal at a select data track offset from a previously-written to data track of the storage medium, where the pulsed input signal has select amplitude and duty cycle to simulate a response signal, and further locking in an amplitude with respect to the heater frequency, can lead to a determination of level of heater power for initiating contact between the transducing head and the storage medium.

Abstract: A data storage device is disclosed comprising a head actuated over a disk, wherein the head comprises a fly height actuator (FHA). A FHA control signal is applied to the FHA, wherein the FHA control signal comprises a DC component and an AC component. A fly height metric is measured representing a fly height of the head over the disk for different levels of the DC component. A modulation amplitude of the fly height metric is detected, and a minimum in the modulation amplitude of the fly height metric is detected.

Abstract: Some embodiments involve a method of managing power for a first multiple-data-storage-devices enclosure. The method can include: checking out a first token over a network connection from a token pool shared by multiple-data-storage-devices enclosures including the first enclosure, wherein each token of the token pool is available to be checked out by a single device and wherein the enclosures share power drawn from a power supply; after checking out the first token, initiating activation of a data storage device within the first enclosure; monitoring power consumption within the first enclosure; and releasing the first token back to the token pool when the power consumption in the first enclosure substantially reaches a steady-state after the activation of the data storage device is initiated.

Abstract: An apparatus and associated method contemplating a head gimbal assembly (HGA) and a bridge circuit including first and second microactuators attached to the HGA. Computation logic is connected to the bridge circuit and configured to independently measure an electrical output of each microactuator and to sum the electrical outputs to derive a value related to a vertically dominant modulation mode of the HGA.

Abstract: A data storage device is disclosed comprising a head actuated over a disk, and a sensor configured to generate a sensor signal representing at least one of a shock and a thermal popping affecting the data storage device. The sensor signal is first filtered based on a first frequency range corresponding to the shock to generate a shock signal, and second filtered based on a second frequency range corresponding to the thermal popping to generate a pop signal, wherein the second frequency range is different from the first frequency range. The shock signal and the pop signal are individually processed, for example, to log a disturbance event, to abort a write operation, or to generate a feed-forward servo compensation signal.

Abstract: A data storage device is disclosed comprising a disk, a head for accessing the disk, and a sensor for generating an alternating sensor signal. The sensor is disconnected from an input of a sensing circuit and while the sensor is disconnected an alternating calibration signal is injected into the input of the sensing circuit, wherein the alternating calibration signal comprises a predetermined offset and amplitude. A response of the sensing circuit to the alternating calibration signal is evaluated to detect at least one of an offset and a gain of the sensing circuit.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a first region and a second region, a head configured to record write data to the disk, a buffer configured to store the write data up to a first capacity, and a controller configured to obtain a first processing amount based on a time to save the write data to the first region by the head and a second processing amount improved by saving the write data from the buffer to the first region, compare the first processing amount with the second processing amount, and determine whether the write data should be saved to the first region, based on a result of the comparison between the first processing amount and the second processing amount.

Abstract: A magnetic disk apparatus of one of the embodiments stores read position dependency information on read signal quality of a data region at a first track and measures the read signal quality at a predetermined radial position in a second data region of a second track different from the first track. A positioning error of the second data region is determined based on the read position dependency information and the read signal quality at the predetermined radial position. Data is recorded in a recording target data region in a shingled recording so as to prevent data written in the second data region from being overwritten by data in a recording target data region adjacent to the second data region by using the determined positioning error.

Abstract: An apparatus comprises circuitry configured to apply an AC signal having a frequency to one of a slider of a recording head and a magnetic recording medium. The applied AC signal causes an oscillation in an electrostatic force and clearance between the slider and the medium at the frequency of the AC signal. A thermal sensor is configured to generate a sensor signal at the AC signal frequency in response to sensing changes in temperature resulting from the oscillating clearance. A detector is coupled to the circuitry and the thermal sensor. The detector is configured to detect one or both of head-medium spacing changes and head-medium contact using a phase of a first harmonic or an amplitude of a second harmonic of the thermal sensor signal.

Abstract: According to one embodiment, a magnetic disk device includes a disk including a tracks including a servo region, a light irradiator configured to irradiate the disk with light and heat the disk with the light, a head including a write head configured to write data in a range irradiated and heated with the light, and a read head configured to read data from the tracks, a controller configured to write first data to be used for offset detection in a first region of the tracks, read the first data from the first region with reference to servo data in the servo region, detect an offset of the read head based on an amplitude of a first signal of the first data, and control a position of the read head based on the offset.