Abstract: Disk drive pre-amplifier output stage circuitry is presented including a high pass input filter for removing DC offsets from differential read data signals and providing an input to AB drivers of the output stage, in which an offset test circuit selectively drives the high pass filter output nodes according to the offset at the filter input to facilitate measurement of the preceding circuit offset at the driver output terminals, and a common mode regulator circuit regulates common mode voltages at the first and second driver output nodes to a predetermined value in read and write modes.

Abstract: Technologies are described herein for detecting adjacent track interference in a storage device using a size-adjustable sliding window. A value for an inter-track interference factor associated with at least one adjacent track is determined for a first area of a data track of the storage device. The first area may encompass a plurality of sectors of the data track. Next, it is determined whether the value of the calculated inter-track interference factor is greater than a threshold value, and if so, an indication of inter-track interference corresponding to the first area is stored in the storage device.

Abstract: A disk controller for a hard disk drive includes a disk formatter interfaced via an NRZ bus to a read channel for the disk. The disk formatter includes an LFSR accumulator coupled to the NRZ bus, as well as an LSFR generator that generates synthetic test data for the disk formatter. Under control of a test flag which signifies a test mode, the LSFR generator generates synthetic test data, which is used by the disk formatter to drive the NRZ bus. The LSFR accumulator accumulates data on the NRZ bus, together with data on servo information and sector information. An interface is provided through which the accumulated information is provided to test equipment, for offline analysis of the accumulated information, so as to confirm proper operation of the disk subsystem and/or to detect failures therein.

Abstract: A method, apparatus, and system are provided for implementing a power-on spin-torque oscillator (STO) oscillation checker to monitor STO resistance to identify STO oscillation with microwave assisted magnetic recording (MAMR) hard disk drives (HDDs). An amplitude modulated write coil drive current is applied to the write coil in the presence of a DC bias current applied to the STO. The amplitude modulated write coil drive current modulates the STO resistance monitored using an amplifier circuit to identify STO oscillation, used to ensure stable MAMR HDD write operation.

Abstract: In one implementation, a method and apparatus is provided for determining an active fly height setting for a transducer head from samples collected from a proximity sensor during less than a single revolution of a disc. Implementations of the method and system use adaptive discrete wavelet transform parameters generated from the collected samples to determine an active fly height setting for a transducer head.

Abstract: A servo system includes a detector circuit operable to apply a data detection algorithm to digital data to yield hard decisions, a convolution circuit operable to yield ideal digital data based on the hard decisions and on target values, a subtraction circuit operable to subtract the ideal digital data from the digital data to yield an error signal, a scaling circuit operable to scale the error signal to yield a scaled noise signal, an adder operable to add the scaled noise signal to the digital data to yield noise-added digital data, and a second detector circuit operable to apply a second data detection algorithm to the noise-added digital data to yield output hard decisions.

Abstract: The disclosure is directed to a system and method of determining signal quality based upon at least one of: a comparison of energy content of the signal to a threshold energy content, a comparison of energy content of the fundamental harmonic of the signal to a specified percentage of the energy content of the signal, and a comparison of a difference between phase of the signal and a target phase to a threshold phase difference.

Abstract: Magnetoresistive (MR) bias is dynamically controlled in a tape drive using a processor device. Median tape head amplitude is monitored during a calibration operation, as measured across all tracks of the tape head, against predetermined thresholds of the tape drive for determining if the median tape head amplitude is below the threshold value. Upon determining the median tape head amplitude is below the threshold value during the calibration operation, a reference MR bias and a MR bias range is dynamically adjusted, during the calibration operation, for increasing the median tape head amplitude.

Abstract: In one embodiment, a method for iterative read channel operation includes executing digital front-end (DFE) functions on signal samples employing decisions provided by a detector executing a detection algorithm, executing an error correcting code (ECC) decoding algorithm on the signal samples using a decoder employing the decisions provided by the detector to generate decisions provided by the decoder, storing the signal samples and the decisions provided by the detector and the decoder, and in an iterative process: executing the DFE functions on the signal samples employing the decisions provided by the decoder, executing the detection algorithm on the signal samples using the detector employing the decisions provided by the decoder to regenerate the decisions provided by the detector, executing the decoding algorithm using the decisions provided by the detector to regenerate the decisions provided by the decoder, and outputting decoding information when the decoding algorithm produces a valid codeword.

Abstract: A method for measuring noise of a magnetic head includes setting a plurality of threshold values, applying bias current or voltage to a read element of the magnetic head, applying an external transverse magnetic field to the magnetic head, amplifying output signal from the read element to produce an amplified signal, filtering the amplified signal to produce a filtered signal, generating an enable signal for each threshold value in a predetermined time window by a counting control means with input signals which include the filtered signal and the threshold value, measuring the cumulative time duration of each enable signal, making an amplitude-duration distribution according to the cumulative time durations and the threshold values, calculating a plurality of parameters according to the amplitude-duration distribution and analyzing the parameters with a plurality of predetermined criteria to determine the defects of the magnetic head.

Abstract: According to one embodiment, any of a first process to perform a write retry to a write target track, a second process to perform the write retry and perform reading for data verification to an adjacent track, and a third process to perform the write retry and write data of the adjacent track to another track is executed based on a result of comparison between an offtrack amount and a plurality of different slice values.

Abstract: The embodiments disclose an orientation control bias point coupled to a magnetic index mark and having a bias point offset set at predetermined coordinates configured to substantially prevent concentricity run-out.

Abstract: A hard disk drive has disks with data sector preambles that allow for inter-track interference. The same data sector preamble is used for all data sectors in a track but the preamble in each track is different from the preamble in radially adjacent tracks. In a first embodiment each preamble includes a synchronization field (SF) and synchronization mark (SM) that are the same in each track but different from the SF and SM in radially adjacent tracks. Only two unique SFs and two unique SMs are required, with the two SFs and two SMs alternating in radially adjacent tracks. In a second embodiment the preambles are “integrated”, meaning that the preamble is a sequence of bits that does not include separate dedicated fields, like SF and SM. The preamble bit sequences are decoded using matched filters to provide bit synchronization and start-of-data information.

Abstract: According to one embodiment, a magnetic disk apparatus includes a plurality of magnetic disks, a plurality of heads which execute recording or reading with respect to the magnetic disks, a plurality of sensors provided in each of the heads and output a signal in accordance with a flying height of the heads from the magnetic disks, a writing module which simultaneously writes servo data in the plurality of magnetic disks by using the plurality of heads, and a control module which simultaneously executes a process for detecting a crash of the heads into the magnetic disks for the plurality of heads based on each output signal of the plurality of sensors when the servo data is written.

Abstract: Track placement on a disk of a Data Storage Device (DSD) including writing test data in a plurality of sectors in a test track on the disk. An adjacent track on the disk is written offset from the test track by an offset distance. Data is read from the test track from an Off-Track Read Capability (OTRC) position outside of the test track. An OTRC value is determined for each sector of the plurality of sectors by varying the OTRC position and determining whether the sector meets a criterion for correctly reading data from the sector. An average OTRC value and a standard deviation are calculated for the plurality of sectors. If it is determined that the average OTRC value is greater than or equal to the predetermined multiple of the standard deviation of the OTRC values, the adjacent track is rewritten at a decreased offset distance.

Abstract: Systems and techniques relating to storage devices, such as storage devices that employ Shingled Magnetic Recording (SMR), can include a device, which includes: circuitry configured to write stored data and parity data to discrete portions of a Shingled Magnetic Recording (SMR) track in a SMR storage device; and circuitry configured to recover stored data for one of the discrete portions of the SMR track using the parity data and the stored data read from remaining ones of the discrete portions of the SMR track.

Abstract: A hard disk drive has disks with data sector preambles that allow for inter-track interference. The same data sector preamble is used for all data sectors in a track but the preamble in each track is different from the preamble in radially adjacent tracks. In a first embodiment each preamble includes a synchronization field (SF) and synchronization mark (SM) that are the same in each track but different from the SF and SM in radially adjacent tracks. Only two unique SFs and two unique SMs are required, with the two SFs and two SMs alternating in radially adjacent tracks. In a second embodiment the preambles are “integrated”, meaning that the preamble is a sequence of bits that does not include separate dedicated fields, like SF and SM. The preamble bit sequences are decoded using matched filters to provide bit synchronization and start-of-data information.

Abstract: Embodiments of the present invention generally relate to a method for obtaining head/disk clearance based on ECS signal. The ECS is calibrated by applying different interface voltages to cause changes in the head/disk clearance, the ECS signal at each interface voltage is obtained, and the relationship between the change in head/disk clearance and the ECS signal is calculated. From this relationship, the head/disk clearance may be obtained based on ECS signal.

Abstract: The disclosure is directed to a system and method of generating soft-orthogonal syncmarks for at least a first set of tracks and a second set of tracks. Random pairs of sync patterns are searched to identify one or more pairs where the sync patterns of each pair exhibit delta-like autocorrelation and small cross-correlation with each other and with preamble portions of the tracks. Then a pair of sync patterns is selected from the one or more identified pairs, where the selected pair includes sync patterns that are distinguishable from the user data portions of the tracks at least partially based upon a data characteristic of the user data portions of the tracks. The selected pair of sync patterns is then used to generate a first syncmark for the first set of tracks and a second syncmark for the second set of tracks.

Abstract: A tape cartridge library that is equipped with a cleaning device is described. The tape cartridge library essentially includes a plurality of tape cartridges each possessing recording tape media. A plurality of tape drives that read and write data to and from each of the tape cartridges. A tape cleaning drive incapable of transferring data to and from the recording tape media which is independent of the tape drives, the tape cleaning drive disposed entirely within the tape cartridge library. The tape cleaning drive automatically receives one of the tape cartridges and cleans its respective recording tape medium when a predetermined reason for cleaning the tape cartridge is justified.

Abstract: A method and system for a sequence estimation in a receiver, such as for use when receiving a sample of a received inter-symbol correlated (ISC) signal corresponding to a transmitted vector of L symbols, with L being a integer greater than 1, and with symbol L being a most-recent symbol and symbol 1 being least recent symbol of the vector. A plurality of candidate vectors may be generated, wherein element L?m of each candidate vector holding one of a plurality of possible values of the symbol L?m, with m is an integer greater than or equal to 1, and elements L?m+1 through L of each candidate vectors holding determined filler values. A plurality of metrics may be generated based on the plurality of candidate vectors, and based on the generated plurality of metrics, a best one of the possible values of the symbol L?m may be selected.

Abstract: Various approaches, methods, systems, circuits and devices for channel bit density estimation.

Abstract: The disclosure is directed to a system and method of determining signal quality based upon at least one of: a comparison of energy content of the signal to a threshold energy content, a comparison of energy content of the fundamental harmonic of the signal to a specified percentage of the energy content of the signal, and a comparison of a difference between phase of the signal and a target phase to a threshold phase difference.

Abstract: According to one embodiment, a magnetic medium's readback signal samples are processed iteratively to provide dropout mitigation for a read channel by feeding the decoder output decisions back to the read channel front end where they are used to drive the decision-aided digital signal processing functions and control loops. Since data decisions provided by the decoder are typically more reliable than those provided by the detector, a significant performance improvement is obtained. A more reliable operation of the digital front-end signal processing functions in turn allows improvements to the reliability of the decoded data. Usage of Error Correcting Code (ECC) schemes that are soft decodable makes the read channel technique, described according to various embodiments herein, particularly efficient.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of data tracks. A plurality of consecutive data tracks are written, and after writing to the plurality of consecutive data tracks, a first number of the consecutive data tracks are read and a second number of the consecutive data tracks are skipped, wherein the second number of data tracks are interleaved with the first number of data tracks. Defects in the data tracks are detected in response to reading the first number of data tracks.

Abstract: According to one embodiment, a first slider of a disk storage apparatus includes a first head and flies over a first recording surface of a first disk. A heater element in the first head projects the first head toward the first recording surface of the first disk depending on heater power. A controller of the apparatus reduces a value for the heater power from a first value to a second value before performing a seek operation of moving the first head such that the first head moves across a concentric circular area including a protrusion on the first recording surface. The controller measures a wait time needed for a flying height of the first head to increase to a first flying height in response to the reduction and starts the seek operation after the wait time elapses.

Abstract: Techniques for disk scrubbing are described herein. According to one embodiment, for each of the sectors of a storage disk, a read operation is issued to a sector of a first storage disk of a storage system. In response to an error returned from the read operation, it is determined whether the sector is a live sector, first data is generated as random data if the sector is not a live sector, and the first data is written to the sector to trigger a remap process that remaps a logical block address associated with the sector to another physical block address. The remap process increments the reallocated sector count. It is determined whether the first storage disk is vulnerable based on a number of reallocated sectors resulted from the first storage disk based on the remap process, which is performed by internal logic of the first storage disk.

Abstract: A method for detecting a contact event between a transducer and a recording medium is disclosed. The method includes positioning a transducer with respect to a recording medium, where the transducer includes a writer, a reader, a heater, and a thermally responsive sensor. The method further includes applying power to the heater to establish a fly height of the transducer; supplying a bias current through the thermally responsive sensor to generate a bias signal; measuring a root mean square (RMS) voltage VRMS of the thermally responsive sensor based on the bias signal; determining a threshold voltage VT; and detecting a contact event between the transducer and the medium based on VRMS being greater than VT.

Abstract: A data storage device with compensation for coercivity variations in a magnetic disk storage medium is disclosed. Two procedures are executed to perform the coercivity compensation. In a first procedure, typically performed prior to writing of data, the coercivity at a number of locations on the disk is measured and stored. A second procedure writes data to locations on a magnetic disk storage medium having varying coercivities. To maintain writing widths within predefined limits, a writing parameter is varied according to a predetermined relationship between the value of the writing parameter and the coercivity. Choices of writing parameter comprise the writing current and fly height. The method may be employed for both data writing and self-servo writing of servo patterns.

Abstract: A disk drive is disclosed comprising a head actuated over a disk, and control circuitry comprising a first shock detector and a second shock detector. A first number of shock events is detected based on the first shock detector, and when the first number of shock events exceeds an upper event threshold, a sensitivity of the first shock detector is decreased. After decreasing the sensitivity of the first shock detector, a second number of shock events is detected based on the second shock detector operating at a higher sensitivity than the first shock detector. When the second number of shock events falls below a lower event threshold, the sensitivity of the first shock detector is increased.

Abstract: A data storage device includes a recording medium including a data region for recording data and a nonvolatile recording unit distinct from the data region. In response to a request for executing erase processing with respect to the recording medium, first time information corresponding to initiation of the erase processing in the nonvolatile recording unit is stored, the erase processing after storing the first time information is executed, and second time information corresponding to completion of the erase processing is stored in the nonvolatile recording unit.

Abstract: A method comprises generating first and second magnetic field components in a magnetic medium, the second magnetic field component substantially opposite the first. A pattern is written onto the magnetic medium, and a signal is generated by reading the pattern. The magnitude of the second magnetic field component is controlled based on an asymmetry of the signal.

Abstract: A read channel of a storage device. The read channel includes a data generator configured to generate a test symbol. An encoding circuit in a write path of the read channel is configured to encode the test symbol as a write signal and provide the write signal to a preamplifier circuit to be amplified by the preamplifier circuit. A decoding circuit in a read path of the read channel is configured to receive the write signal as amplified by the preamplifier circuit and decode the write signal as amplified by the preamplifier circuit to determine a received symbol corresponding to the encoded test symbol. A comparator is configured to compare the received symbol to the test symbol and output, based on the comparison of the received symbol and the test symbol, an indication of whether the preamplifier circuit is operational.

Abstract: A method of radially positioning a heat assisted magnetic recording (HAMR) head writes data to a first band, wherein a radial position of the HAMR head within each data track is defined by a positional bias and a track location. A determination is made regarding whether a threshold has been reached with respect to the first band. If the write threshold has been reached with respect to the first band, then the positional bias associated with the first band is modified to evenly distribute thermal exposure of data tracks in the first band.

Abstract: Embodiments of the invention relate to a hard disk drive (HDD) formatted with at least two surfaces, each of the surfaces serviced a write head, each write head configured for the respective surface. At least one of the surfaces of the HDD is serviced by a random block overwrite (RBO) head for an associated surface. Similarly, at least one of the surfaces of the HDD is serviced by a shingled magnetic recording (SMR) head for an associated SMR surface. The properties of both the RBO and SMR surfaces are retained, and at the same time leveraged to maximize data density and write performance in a single HDD.

Abstract: A magnetic storage system includes a magnetic storage medium, a random-access memory (RAM), and a controller. The controller interfaces with both the magnetic storage medium and the RAM, and implements a refresh algorithm that determines when a data track on the magnetic storage medium should be refreshed. The controller maintains in the magnetic storage medium a plurality of finer-granularity damage count tables, each table having finer-granularity damage counts each representing damage to one or more sectors within each of the plurality of tracks associated with the table. The controller maintains in RAM a plurality of track-level damage count values, each associated with one of the plurality of data tracks and representing estimated damage to one of the plurality of data tracks. Based on data written to the plurality of data tracks, the controller utilizes finer-granularity damage count tables stored in the magnetic media to update the track-level damage.

Abstract: According to one embodiment, there is provided a method, implemented in a magnetic disk drive, for adjusting a linear recording density. The method obtains a first flying-dependent error sensitivity for each of two or more heads. The first flying-dependent error sensitivity represents a change in read error rate corresponding to a change in flying height of the head during write. In addition, the method reduces the linear recording density of a first recording surface associated with a first head of the two or more heads if the first flying-dependent error sensitivity is a second flying-dependent error sensitivity higher than a threshold and corresponds to the first head.

Abstract: Technologies are described herein for determining the linear storage density of data tracks on a recording media of a storage device while compensating for segments of the recording media with poor bit-error rates. The sectors of the data track are grouped into a plurality of segments and a bits-per-inch capability (“BPIC”) value is determined for each of the plurality of segments based on a target bit-error rate. The lowest segment BPIC value from amongst the plurality of segments is then determined as well as an average BPIC value for the entire data track. The final BPI value for the data track is determined based on the average BPIC value and the lowest segment BPIC value.

Abstract: Systems and methods are provided for calibrating signals retrieved from a storage device using a first reader and a second reader. The systems and methods further include reading a first signal using the first reader and a second signal using the second reader. Control circuitry computes a calibration metric associated with the first reader and the second reader based on the combination of the first signal and the second signal. At least one of the first signal and the second signal is subsequently decoded based in part on the computed calibration metric.

Abstract: In one embodiment, a method includes updating a standard deviation or a variance based on a current position error signal sample, where a smoothing factor applied to a subsequent calculation of the standard deviation or variance is dynamically altered based at least in part on whether a current value of the standard deviation or the variance is above or below a specified value. A determination is made as to whether the standard deviation or the variance exceeds a predetermined threshold. A stopwrite threshold is determined based on the standard deviation or the variance when the standard deviation or the variance exceeds the predetermined threshold. A determination is made as to whether the current position error signal sample exceeds the stopwrite threshold. Writing is disabled when the current position error signal sample exceeds the stopwrite threshold. Writing is enabled when the current position error signal sample does not exceed the stopwrite threshold.

Abstract: A system and method for predicting the likelihood of failure of the individual sectors of a magnetic storage disk based upon the monitoring of adjacent sector performance in responding to access requests. The prediction for a specific target sector's fidelity can be made through the gathering of sector performance data that occurs during normal read/write actions to the adjacent sectors, without a recent access request necessarily being made to the target sector. Scrubbing of the sectors can also be directed based upon the needed sector access data for target sector fidelity prediction.

Abstract: Technologies are described herein for recovering an instable head in a storage device using an internal head heater. An instability in the reader head may be detected, and, in response to detecting the instability, a thermal shock may be applied to the reader head utilizing the head heater to recover the head.

Abstract: According to at least one embodiment, a read/write apparatus includes a read module and a positioning module. The read module reads data of a predetermined data track using a read head. The positioning module positions the read head in accordance with an index indicating how much the read head reads data of a neighboring data track of the predetermined data track when the read head reads data of the predetermined data track.

Abstract: A method of storing data in a storage medium includes determining a compensation unit for a portion of the storage medium, reading a first set of bit values from the portion of the storage medium, determining a compensation value based at least in part on an erroneous bit value of the first set of bit values and the compensation unit, and storing the compensation value in association with the portion of the storage medium.

Abstract: A method, apparatus, and system are provided for implementing a power-on spin-torque oscillator (STO) oscillation checker to monitor STO resistance to identify STO oscillation with microwave assisted magnetic recording (MAMR) hard disk drives (HDDs). A changing bias current is applied to the STO in the presence of constant write drive current. The STO bias current is changed to observe sudden changes in STO resistance monitored using a differentiator circuit to identify STO oscillation, used to ensure stable MAMR HDD write operation.

Abstract: According to one embodiment, there is provided a method for detecting touchdown of head in a disk storage apparatus. The disk storage apparatus includes the head. The head includes a write element, a read element, a head disk interference (HDI) sensor, and a heater element. The HDI sensor detects thermal interference between the head and the disk. The method supplies alternating-current heater power to the heater element. The method increases the heater power in a step-by-step manner. The method further detects a phase of an output signal from the HDI sensor corresponding to the increased heater power, and detects the touchdown based on a change in the detected phase.

Abstract: A scissor style magnetic sensor having a novel hard bias structure for improved magnetic biasing robustness. The sensor includes a sensor stack that includes first and second magnetic layers separated by a non-magnetic layer such as an electrically insulating barrier layer or an electrically conductive spacer layer. The first and second magnetic layers have magnetizations that are antiparallel coupled, but that are canted in a direction that is neither parallel with nor perpendicular to the air bearing surface by a magnetic bias structure. The magnetic bias structure includes a neck portion extending from the back edge of the sensor stack and having first and second sides that are aligned with first and second sides of the sensor stack. The bias structure also includes a tapered or wedged portion extending backward from the neck portion.

Abstract: A data storage device and method for enabling dynamic fly height control which is insensitive to off-track motions is described. In some embodiments, a hard disk drive acquires signal data from neighboring overlapping tracks which are unwritten, thermally erased, or AC demagnetized. Side-to-side (off-track) positional errors or oscillations of the read head do not affect the signal which arises solely from the magnetic domains on the disk. Thus, signal variations may only arise from changes in the fly height. In other embodiments, neighboring overlapping data tracks are prewritten with reference data. The width of the neighboring overlapping tracks exceeds any expected side-to-side positional errors of the read head, thus signal variations may only arise from changes in the fly height. For all embodiments, the noise or reference data signal may serve as a reliable dynamic measure of the fly height with no effects arising from off-track motions.

Abstract: Systems and method relating generally to data processing, and more particularly to systems and methods for determining head stability.

Abstract: Various approaches, methods, systems, circuits and devices for channel bit density estimation.