Abstract: A method in one embodiment includes receiving a command to perform at least one of a refresh operation and a verification operation on a media cartridge having a tape wrapped around a spool; mounting the media cartridge in a tape drive; starting execution of the refresh and/or verification operation; aborting execution of the refresh and/or verification operation upon occurrence of a predetermined event. A method in another embodiment includes receiving an instruction to perform a verification operation on a media cartridge having a tape wrapped around a spool; unwrapping at least some of the tape from the spool; after the unwrapping, wrapping at least some of the tape back onto the spool; during at least one of the unwrapping and wrapping, performing a verification operation; terminating execution of the verification operation when a drive error is detected; outputting an indication of a media error when a media error is encountered.

Abstract: Provided are magnetic read-write inspection apparatus and inspection method allowing measurement and inspection again by a sector servo system even when a magnetic disk measured and inspected by the sector servo system is detached from the inspection apparatus and re-mounted. A data write unit writes a servo pattern signal in a predetermined track range of the disk, writes an inspection test pattern signal onto an inspection track by performing sector-servo-system-based positioning and concentrically writes an eccentricity learning pattern onto an eccentricity learning track which is different from the inspection track. An eccentric quantity learning unit calculates an eccentric quantity of the disk from a read signal detection position by reading out the eccentricity learning pattern without using servo information. An eccentric quantity correction unit controls shaking of a magnetic head so as to cancel the calculated eccentric quantity when reading out a test signal from the disk.

Abstract: A disk drive is disclosed comprising a disk surface comprising a plurality of tracks, each track comprising a plurality of servo sectors. The disk drive further comprises a head coupled to a distal end of an actuator arm, and a voice coil motor (VCM) and a microactuator operable to actuate the head over the disk surface. The head is first servoed in response to the servo sectors, and after first servoing the head, a manufacturing procedure is executed by controlling the VCM and the microactuator to servo the head while accessing the disk surface. After executing the manufacturing procedure, the head is second servoed in response to the servo sectors, and the microactuator is evaluated in response to the first and second servoing.

Abstract: A shingled magnetic recording (SMR) hard disk drive (HDD) essentially eliminates the effect of far track erasure (FTE) in the boundary regions of annular data bands caused by writing in the boundary regions of adjacent annular data bands. The extent of the FTE effect is determined for each track within a range of tracks of the track being written. Based on the relative FTE effect for all the tracks in the range, a count increment (CI) table or a cumulative count increment (CCI) table is maintained for all the tracks in the range. For every writing to a track in a boundary region, a count for each track in an adjacent boundary region, or a cumulative count for the adjacent boundary region, is increased. When the count reaches a predetermined threshold the data is read from that band and rewritten to the same band.

Abstract: A method for testing a hard drive includes determining a first partial bit error rate (PBERT) value of a hard drive at a first temperature and a second PBERT value of the hard drive at a second temperature. The method includes determining a PBERT minimum based on the first and second PBERT values, and comparing the PBERT minimum to a first PBERT minimum limit. The method includes determining a PBERT ratio based on the first and second PBERT values if the PBERT minimum is greater than or equal to the first PBERT minimum limit. The method includes comparing the PBERT ratio to a PBERT ratio limit, and comparing the PBERT minimum to a second PBERT minimum limit if the PBERT ratio is greater than the PBERT ratio limit. The method includes generating a failure indicator if the PBERT minimum is less than the first and/or second PBERT minimum limit.

Abstract: Embodiments of the present invention help to reduce damage of a head element portion or a magnetic disk in a procedure for specifying a heater power value for adjusting a clearance between the head element portion and the magnetic disk. In an embodiment of the present invention, an HDC/MPU sequentially performs data writing and reading while increasing heater power. The HDC/MPU further determines whether or not a head slider has retrieved the data properly. When the data cannot be retrieved properly, the HDC/MPU specifies a heater power value in a normal operation based on the heater power value at which the data could not be retrieved properly.

Abstract: A shingled magnetic recording (SMR) hard disk drive (HDD) essentially eliminates the effect of far track erasure (FTE) in the boundary regions of annular data bands caused by writing in the boundary regions of adjacent annular data bands. The extent of the FTE effect is determined for each track within a range of tracks of the track being written. Based on the relative FTE effect for all the tracks in the range, a count increment (CI) table or a cumulative count increment (CCI) table is maintained for all the tracks in the range. For every writing to a track in a boundary region, a count for each track in an adjacent boundary region, or a cumulative count for the adjacent boundary region, is increased. When the count reaches a predetermined threshold the data is read from that band and rewritten to the same band.

Abstract: A system and method for monitoring fly height between a magnetic recording medium and a transducing head. In a first exemplary embodiment, magnetic spacing change value is calculated using media noise on the recording medium (instead of prerecorded tones) to provide a broadband frequency distribution that results in improved Wallace equation accuracy. In a second exemplary embodiment, a magnetic spacing change value is acquired by any suitable method but is adjusted as necessary to reflect transducing head wear, thus providing a methodology for calculating changes in fly height by taking into account the signal loss that is attributable to wear. In this way, a basic understanding of the mechanism causing changes in magnetic spacing is achieved.

Abstract: A hard disk drive (HDD) minimizes the effects of far track erasure (FTE) by counting the number of writes to the data tracks and incrementing counters based on the known effect of FTE on each track. The extent of the FTE effect is determined for each track within a range of tracks of the track being written, and based on the relative FTE effect for all the tracks in the range a count increment (CI) is determined for each track within the range. A counter is maintained for each track. For every writing to a track, a count for each track within a range of the track being written is increased by the CI value associated with the track number within the range. When the count value for a track reaches a predetermined threshold the data is read from that track and rewritten, preferably to the same track.

Abstract: A method of refreshing data on a hard disk drive configured to carry out commands issued by a host that comprises tracking run-time conditions related to patterns of host command activity on the hard disk drive; selecting an entry from a high priority pool that is configured to hold a predetermined maximum number of entries, each entry comprising a plurality of tracks having been designated as being eligible for a high priority refresh operation as a result of the host command activity; refreshing data stored on at least one track of the selected entry; pausing the refreshing for a period of time equal to a throttle interval to process at least one command issued by the host before returning to the selecting or to the refreshing, and periodically modifying a value of the throttle interval depending upon the tracked run-time conditions.

Abstract: Described are embodiments of an invention for customizing the range of acceptable write conditions to a tape of a tape cartridge that contracts or expands laterally based on environmental conditions. The tape drive utilizes servo information to determine if the tape has expanded or contracted from the nominal dimension and to determine the magnitude of the expansion or contraction. In the case of expansion, the magnitude of the determined expansion and the stored maximum amount of contraction must be below a predetermined threshold value to allow a write. In the case of contraction, the magnitude of the determined contraction and the stored magnitude of expansion must be below the same predetermined threshold value to allow a write. If the determined magnitude of contraction or expansion is greater than the stored magnitude of contraction or expansion, respectively, then the new extreme is stored.

Abstract: Various embodiments of the present invention provide systems and methods for calculating and/or modifying fly height. For example, a circuit for calculating fly height is disclosed that includes: a first pattern detector circuit, a second pattern detector circuit, a first pattern fly height calculation circuit, a second pattern fly height calculation circuit, a first averaging circuit, a second averaging circuit, and a combining circuit.

Abstract: A slider tester includes a disk, movable table, table drive mechanism, guide member, etc. A plurality of suspensions are mounted on the movable table. A slider is mounted on each suspension. A guide member can support respective lift tabs of the suspensions. The guide member includes a first guide surface, second guide surface, and opening arranged in a track width direction of the disk. When any of the lift tabs gets into the opening as the movable table moves in the track width direction of the disk, the slider is dropped toward a recording surface of the disk.

Abstract: A system including a hard disk control circuit, a read channel circuit, and a preamplifier circuit. The hard disk control circuit is configured to generate a first symbol. The read channel circuit configured to encode the first symbol to generate an encoded symbol. The preamplifier circuit configured to operate in a loopback mode. While operating in the loopback mode, the preamplifier circuit is configured to amplify the encoded symbol and transmit the encoded symbol back to the read channel circuit. The read channel circuit is configured to decode the encoded symbol to generate a second symbol and provide the second symbol to the hard disk control circuit. The hard disk control circuit is configured to perform a comparison between the first symbol and the second symbol and generate an indication of whether the preamplifier circuit is operating properly based on the comparison between the first symbol and the second symbol.

Abstract: A magnetic recording/reproducing apparatus 100 includes: a magnetic head 1; a magnetic recording medium 2; a spindle 3 and a spindle motor 4; a suspension arm 5; a voice coil motor 6; and a control unit 7. The control unit 7 has: a motor driver 8; a head amplifier 9; a read/write channel 10; a laser driver 11; and a controller 12. The controller 12 has: a preliminary recording unit 13; a judgment unit 14; an extraction unit 15; a drive condition determining unit 16; and a preliminary recording terminating unit 17. Based on a reproduction signal evaluation value obtained using these units and a predetermined reference value, a drive condition is determined which is suitable for recording onto the magnetic recording medium 2.

Abstract: A hard disk drive or other disk-based storage device comprises a storage disk, a read/write head configured to read data from and write data to the disk, and control circuitry coupled to the read/write head and configured to process data received from and supplied to the read/write head. The control circuitry comprises calibration circuitry configured to vary a phase of a clock signal as a test pattern is written to the storage disk as part of a calibration procedure, and disk locked clock circuitry coupled to the calibration circuitry and configured to obtain phase lock between the clock signal and a timing pattern on a surface of the storage disk. The calibration circuitry is further configured to determine an initial phase update value to be applied by the disk locked clock circuitry in a control loop as the phase of the clock signal is varied as part of the calibration procedure.

Abstract: According to at least one embodiment, a magnetic disk apparatus includes a disk, a random number generator, a determination module, and a refresh module. The disk includes a plurality of tracks. A random number generator generates a random number within a range of N integers in accordance with writing to a first area of a first track of the plurality of tracks. A determination module determines whether the generated random number includes a predetermined number. A refresh module refreshes a second area of a second track near the first track based on a result of determination of the determination module. The second area corresponds to the first area.

Abstract: According to at least one embodiment, a magnetic disk apparatus includes a magnetic disk, a nonvolatile memory, a determination module, a write module, and a read module. The determination module determines whether the off-track write occurs on a first data sector during a write mode. The write module writes first data in the nonvolatile memory if the determination module determines that the off-track write occurs on the first data sector. The read module reads the first data from one of the magnetic disk and the nonvolatile memory based on a determination result of the determination module.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is discussed that includes: a servo address mark count circuit, a user sync mark count circuit, and an offset calculation circuit. The servo address mark count circuit is operable to provide: a first count corresponding to a first servo address mark within a first track of a storage medium, a second count corresponding to a second servo address mark within the first track, a third count corresponding to a third servo address mark within a second track of the storage medium, and a fourth count corresponding to a fourth servo address mark within the second track. The user sync mark count circuit is operable to provide: a fifth count corresponding to a first user sync mark within the first track, and to provide a sixth count corresponding to a second user sync mark within the second track.

Abstract: A tape drive is disclosed. The tape drive determines a current tape width and writes data to the tape as well as the current tape width. The tape width written to the tape is associated with the data. When reading data from a tape the tape drive reads the stored tape width and adjusts the current tape width to match the stored tape width before reading the data associated with the stored tape width.

Abstract: A method for efficiently rewriting data to tape is disclosed herein. In one embodiment, such a method includes writing a data set to tape, the data set comprising S sub data sets of fixed size, each sub data set comprising N code word interleaves (CWIs). The method further includes reading the data set while writing it to the tape to identify faulty CWIs. While reading the data set, the method buffers the faulty CWIs (such as by storing, identifying, and/or marking the faulty CWIs) for later retrieval. When the end of the data set is reached, the method writes corrected versions of the faulty CWIs to the end of the data set. A corresponding apparatus is also disclosed and claimed herein.

Abstract: A data-overwriting technique that facilitates determining whether data is new or old. A tape recording apparatus includes: a receiving unit for receiving information on overwrite starting position and an overwrite request; a trying unit for trying to determine a beginning position of a data unit; an overwrite executing unit for executing overwriting from the determined overwrite starting position in response to a success of the determination by the trying unit; and a type judging unit for judging whether the data unit that is recorded at the overwrite starting position is a null data unit or not in response to a failure of the determination by the trying unit. The trying unit responds to judgment that the data unit is the null data unit by determining a beginning of a data unit following the data unit as the overwrite starting position.

Abstract: A disk drive is disclosed comprising a disk including a plurality of tracks, a head actuated over the disk, and control circuitry. The control circuitry is operable to: write a target track including a plurality of data wedges; determine optimization metrics for the data wedges of the plurality of data wedges as the data wedges are read; store the optimization metrics for the data wedges from the target track; and remove a first portion and a second portion of the optimization metrics such that a remaining portion of the optimization metrics remains. Further, the control circuitry is operable to calculate an average optimization metric value for the remaining portion of optimization metrics for use in read channel optimization.

Abstract: A tape drive is disclosed. The tape drive determines a current tape width and adjusts the length of a tape head to more closely match the current tape width. The tape drive adjusts the length of the tape head by controlling the power to a heating element coupled to the tape head.

Abstract: Approaches for a distributed temperature detector architecture in a head disk interface system of a hard-disk drive (HDD). A HDD may include a read/write head comprising a read element and a write element and a read/write integrated circuit (IC). The read/write head may comprise (a) a first temperature sensor that is located relatively near an air bearing surface (ABS) of the read/write head and (b) a second temperature sensor that is offset from the ABS. The read/write IC is configured to detect when the read/write head makes physical contact with a disk based on a difference in temperature measured by the first and second temperature sensor. The first and second temperature sensors form a bridge circuit, such as a Wheatstone bridge, with a first IC resistor and a second IC resistor that both reside in the read/write IC, allowing the temperature of the read/write head to be accurately measured.

Abstract: In one embodiment, a system includes a medium, a magnetic head having a write element adapted for writing data to the medium, a MAMR element and/or a TAMR element adapted for assisting recording on the medium, the MAMR element having a microwave-generating portion that receives current for operation thereof, the TAMR element having a localized heat-generating portion that receives current for operation thereof, and a read element adapted for reading data from the medium, a device adapted for measuring environmental conditions relating to the TAMR/MAMR elements and the medium, and a controller adapted for controlling operation of the magnetic head and adjusting operating parameters of the system based on the environmental conditions. The environmental conditions include temperature, a reproduced signal of the read element, and/or clearance between the TAMR/MAMR elements and the medium. The operating parameters include the clearance, amount of current injected to the TAMR/MAMR elements, and/or write current.

Abstract: A method and apparatus for writing data to a tape is disclosed. A plurality of data segments are written onto a tape simultaneously. Any data segments written to the tape that needs to be rewritten are identified. Each data segment that needs to be re-written is accumulated. The accumulated data segments are written to tape when a full set of data segments have been accumulated. The re-written data segments each have a first field in a header that designates itself and a second field in the header that designates a second re-written data segment.

Abstract: A magnetic recording apparatus includes: a magnetic recording medium having a recording surface on which a plurality of magnetic recording cells magnetically isolated from each other are arranged; a magnetic writing element recording information to the magnetic recording cells under a condition in accordance with setting information; a magnetic reading element reproducing information recorded in the magnetic recording cells; a memory storing the setting information for writing; and a processor for executing a program code.

Abstract: Methods and apparatus are provided for processing a signal in a read channel using an oversampled analog to digital conversion. An oversampled analog to digital conversion is performed on an analog input signal to generate a plurality of digital samples corresponding to the analog input signal for a given bit interval. A data detection algorithm can then be applied on one or more of the digital samples to obtain a detected output. The oversampled analog to digital conversion simplifies the analog design by transferring at least a portion of the equalization and/or filtering processes to the digital domain.

Abstract: A “write-squeeze-verify” method is used for verification of the data that has been written in the annular bands of a shingled magnetic recording disk drive. The writing of data along a track overwrites a portion of the previously written track and thus “squeezes” the data of the previously written track to thereby form a “shingled data track” (SDT). The data in each SDT is read back and verified by performing an error correction check using error correction bits associated with the data written in the SDT, or by comparing the readback data with the data stored in memory. If the data read back is not verified, a write error counter is incremented and a write error frequency is calculated. One or more attempts to write the data can be performed. If the data in the SDT cannot be verified after the attempted rewrite(s), then a “re-try fail” is reported.

Abstract: A synchronizing circuit compatible with a quad switching scheme in a digital-to-analog converter (DAC) to synchronize turning on or off of switches for steering current to a differential output. The synchronizing circuit receives signals from a decoder and synchronizes control signals to the switches by a clock signal. In one embodiment, the synchronizing circuit includes a predictor circuit and a latch circuit. The latch circuit may include four sets of cross-coupled inverters where a set of cross-coupled inverters are activated at a time. By using the synchronizing circuit in conjunction with the quad switching scheme, linearity of analog output from the DAC can be improved and data dependent noise in the analog output can be removed or reduced.

Abstract: A magneto-impedance sensor element is formed in a planar type structure in which an amorphous wire is incorporated in a substrate. The magneto-impedance sensor element includes a nonmagnetic substrate, an amorphous wire arranged in an aligning direction of a planar pattern that forms a detecting coil, a spiral detecting coil formed of a planar pattern and a cubic pattern on an outer periphery of the amorphous wire, a planar insulating portion that insulates the planar pattern from the amorphous wire, a wire fixing portion to fix the amorphous wire on an upper surface of the planar insulating portion, and a cubic insulating portion that insulates the cubic pattern from the amorphous wire.

Abstract: According to one embodiment, this invention determines whether a maximum value Hmax and minimum value Hmin of an HF signal obtained when a data recording portion is irradiated with a laser having a wavelength of 450 nm or less and an NA of 0.6 or more meet (Hmax?Hmin)/Hmax<0.13 . . . (1), or whether a maximum value Hmax, a minimum value Hmin, and a most frequent voltage value Have of a signal level of an HF signal obtained when a data recording portion is irradiated with a laser having a wavelength of 450 nm or less and an NA of 0.6 or more meet Hmax/Have?1.05 . . . (2) and Hmin/Have?0.90 . . . (3).

Abstract: A method, apparatus and a data storage device are provided for implementing data track pitch adjustment for data written on a recordable surface of a storage device under operational vibration conditions. An operational vibration disturbance spectrum is detected during a write operation and the data track pitch is selectively adjusted based on the detected operational vibration disturbance spectrum. The adjusted track pitch information is saved and used during a read operation.

Abstract: A disc drive system provides increased reliability by detecting and correcting errors associated with bit-patterned media. Write synchronization errors associated with bit-patterned media are addressed by including data storage for temporarily storing data that is being written to the disc drive. The data is read from both the disc drive and the storage medium and compared to detect write synchronization errors. A disc drive system for correcting write synchronization errors includes an encoder, non-volatile storage, and decoder device for implementing a parity-based scheme for increased reliability. Data strings being written to the disc drive are combined in an encoder to generate a parity string. The address of the data being written to the disc drive, along with the updated parity string is stored to the non-volatile storage. The data strings are read from the disc drive by the decoder.

Abstract: According to embodiments of the present invention, a data storage device is provided. The data storage device includes a recording channel configured to carry a signal; a detector configured to detect the signal from the recording channel; and a noise prediction circuit configured to predict noise affecting the recording channel and the detected signal based on a noisy channel model. According to further embodiments of the present invention, a method of processing a signal in a data storage device is also provided.

Abstract: Techniques to use a model associating condition of a tape head with tape head usage are described. The tape head is for use in a magnetic tape drive. In examples, a condition of the tape head is determined using a model. In examples, the model fits determined values of the condition parameter.

Abstract: A receiving device may be configured to derive an oversampled dibit pulse response estimate using symbols sampled at substantially the read channel symbol rate of the receiving device. The receiving device may include a data acquisition circuit configured to digitize data derived from a memory medium, a symbol timing loop and read circuit, as well as a dibit pulse estimation circuit configured to estimate the oversampled dibit pulse response using symbols sampled at the read channel rate of the receiving device without disturbing the symbol timing loop and read circuit.

Abstract: Techniques to determine particular bad tapes or tape drives. All tape and tape drive combinations within a system may be obtained. A read error or a write error that occurs with each tape and tape drive combination may be detected, and the read error, the write error, or a parameter may be analyzed to determine the particular tape or the particular tape drive that is bad.

Abstract: A method and apparatus for providing a signal for driving a heating element in a TAR or HAMR enabled disk storage system that includes an optical transducer (or near-field optical source) for further focusing the beamspot of a laser onto a magnetic media, thereby heating the media. The storage system includes a temperature sensor proximate to the near-field transducer which provides a feedback loop to the laser driver to adjust the power of the laser.

Abstract: A disk spindle assembly cartridge is described. The disk spindle assembly cartridge includes a base, a spindle motor attached to the base, a disk seated on the spindle motor, a disk clamp attached to the spindle motor, wherein the disk clamp secures the disk to the spindle motor, and a cover attached to the base. The base is configured to detachably mount a head stack assembly cartridge, where the disk is accessible to a head stack assembly pivotally mounted in the head stack assembly cartridge via an opening defined by the base and the cover.

Abstract: A hard drive component test system is provided. The hard drive component test system includes a rack having multiple test bays with first test sub-assemblies mounted in respective ones of the of test bays. A test control system is electrically coupled to each of the first test sub-assemblies. Each of the test bays is configured to receive a second test sub-assembly and to engage the second test sub-assembly with the first test sub-assembly mounted in the respective bay to form a drive assembly. The test control system is configured to selectively execute a test process on the drive assemblies mounted in the rack.

Abstract: An apparatus is disclosed comprising a thermal sensor operable to detect at least one protrusion defect and at least one recess defect on a disk, the thermal sensor operable to generate a sensor signal. An attack time of the sensor signal is measured when the thermal sensor passes over one of the protrusion defect and the recess defect, and the protrusion defect is discriminated from the recess defect based on the attack time.

Abstract: Searching for patterns stored on a hardware storage device. A method includes, as part of a memory refresh operation, performing a read to read contents of a portion of a memory. The method further includes writing the read contents of the portion of memory back to the portion of memory. The read contents are provided to data comparison logic. Using the data comparison logic; the read contents are compared to predetermined data patterns. A determination is made as to whether or not the contents match at least one of the predetermined data patterns. When the read contents match at least one of the predetermined data patterns, a software readable indicator is provided indicating that the read contents match at least one of the predetermined data patterns. Similar embodiments may be implemented using hard drive head wear leveling operations.

Abstract: A hybrid drive is disclosed comprising a head actuated over a disk comprising a plurality of data sectors, and a non-volatile semiconductor memory (NVSM) comprising a plurality of memory segments. A read command is received from a host to read data from a first data sector. Data is read from the first data sector during a first read operation and a determination is made as to whether the first data sector is suspect. When the first data sector is suspect, the data is written to a first memory segment of the NVSM.

Abstract: Dynamic fly height (DFH) controlled read/write heads using multiple heaters have their heater powers set within a range of ratios that allows minimum clearances to be set between the read-gap and the write-gap and the surface of a disk, thereby providing improved touch-down detection. Determining the correct range of power ratios requires varying the ratio to create an adjustable protrusion profile for the read and write elements in the head and measuring values of the ratio and corresponding values of read gap and write gap clearances that create points of minimum clearance. By adjusting the ratio of power supplied to the heaters, different protrusion profiles can be produced, clearance control for sigma reduction can be obtained and read/write readiness and operation consistency and reliability can be improved.

Abstract: According to one embodiment, a magnetic recording and reproduction device includes a head; a heater configured to heat the head by electric power supplied; a detector provided with a resistive element and configured to detect a contact between the head and a magnetic recording medium by detecting a change in resistance of the resistive element associated with the contact between the head and the magnetic recording medium; and a flying height controller configured to control a flying height of the head from the magnetic recording medium by supplying electric power to the heater to thermally deform the head and to bring the deformed head into contact with the magnetic recording medium so as to determine reference power supplied when the head is in contact with the magnetic recording medium and by supplying electric power to the heater based on the reference power.

Abstract: A data-overwriting technique that facilitates determining whether data is new or old, when reading thereof. A tape recording apparatus includes: a receiving unit for receiving information on overwrite starting position and an overwrite request; a trying unit for trying to determine a beginning position of a data unit based on the information on an overwrite starting position, wherein the data unit is a unit of writing data recorded on a tape medium; an overwrite executing unit for executing overwriting from the determined overwrite starting position in response to a success of the determination by the trying unit; and a type judging unit for judging whether the data unit that is recorded at the overwrite starting position is a null data unit or not in response to a failure of the determination by the trying unit. The trying unit responds to judgment that the data unit is the null data unit by trying to determine a beginning of a data unit following the data unit as the overwrite starting position.

Abstract: A magnetic head slider includes a near-field light generator, an incorporated heater is activated to thermally-expand the magnetic head slider so that a first protrusion is generated on the air bearing surface, and a second protrusion protruding from the first protrusion is generated by a thermal expansion of the near-field light generator. A standard signal is written to a recording medium with a predetermined magnetization. A relation between a residual magnetization of the standard signal and a power of the heater is obtained by lowering the magnetization of the standard signal by heating the recording medium with the near-field light while light output of laser light is maintained to be constant and the power of the heater is varied. Further, a relation between the first spacing and the residual magnetization is obtained.

Abstract: According to one embodiment, a magnetic disk includes a disk, a controller and an indicator module. The disk includes a plurality of data sectors. The controller is configured to control data rewrite for reading a first data block stored in the disk and writing a second data block corresponding to the read first data block to a write destination on the disk. The indicator module is configured to embed an indicator indicative of an attribute relating to data rewrite in each sector data in the second data block written to the write destination when the each sector data is written to the write destination.