Abstract: A magnetic data read circuit includes a differentiation circuit and an integration circuit which are individually connected to a magnetic head, and a means of read judgment for pass/fail judgment on reading operation of magnetic data detected at the magnetic head. The read judgment means has first and second storage sections in which data relating to an output signal of the differentiation circuit and the integration circuit, respectively, are stored. The read judgment section obtains data from at least one of the first storage section and the second storage section and makes a pass/fail judgment on reading operation of the magnetic data. Such a magnetic data read circuit improves accuracy of reading magnetic data stored in a magnetic recording medium from a single transfer of the magnetic recording medium data.

Abstract: According to one embodiment, a disk drive apparatus includes a defect table formed using more than one defect detection standard. Methods and devices are described using different defect detection standards to detect and map defects of different sizes and in specific regions that can affect drive operation. Also, methods and devices are described that provide fast and efficient defect scanning in selected regions due to utilization of error correction systems. Methods are shown where during defect detection a read/write gate assertion is triggered using a servo gate pulse.

Abstract: Embodiments of the invention relate to diagnosing error-correcting retries of an upper system by using a disk drive under control of the upper system. In one embodiment, a microprocessor can operate in any of at least two operation modes. One is normal operation mode while the other is pseudo failure operation mode. Mode switching is made by a switch. Strictly, the pseudo failure operation mode includes three different operation modes: 1) pseudo logical error report mode in which a pseudo logical error is reported to the upper system without performing disk control; 2) pseudo component circuit failure mode in which a control circuit is forced to cause a failure by setting invalid control values to the control circuits; and 3) pseudo interface failure mode in which a pseudo interface failure in the system comprising multiple disk drives is reported by setting an invalid control value to the interface control circuit.

Abstract: A method and apparatus for predicting write failure resulting from flying height modulation and initiating re-writing of data upon occurrence of the predicted write failure is disclosed. According to the present invention, if the slider or transducer flying height modulates during the write process, such modulation is detected, and a rewrite of the same data is forced. A write reassign may be initiated when a thermal signal exceeding the predetermined threshold is detected during the rewrite and/or a read/verify may be initiated after the rewrite.

Abstract: A method for a removable media storage network environment that employs a media management system for managing a removable media system on behalf of client applications, and a media management agent to enhance the management of the removable media system by the media management system. The media management agent operates to determine an operational state of the removable media system, and to enhance an availability and a performance of the removable media system as managed by a media management system, wherein one or more one error recovery techniques are conditionally initiated based on the determined operational state of the removable media system and wherein the media management system is conditionally reconfigured based on the determined operational state of the removable media system.

Abstract: A method of protecting data on a recording medium against an adjacent track erase (ATE) effect, and a recording medium having a program therefor are provided. The method includes accumulating a number of turns of write operations in respective sub-areas, wherein the recording medium is divided into a plurality of sub-areas; and rewriting data on a sub-area of which an accumulated number of turns of write operations is greater than a limited number of turns of write operations. Accordingly, before data written on an adjacent track can be damaged by the ATE effect, data is rewritten and safely preserved.

Abstract: Embodiments of the invention reduce the information (storage) overhead for determining the rotational position of a magnetic disk medium, as well as reducing the rotational position detection time. In one embodiment, a sector servo magnetic disk medium is configured such that: each track is divided into blocks each including a series of sectors; each block stores a positional information bit string as rotational position information; the positional information bit string is made up of a position code and an identification code, the position code including a block number, the identification code being used to identify the start or the end of the position code; and each bit of the positional information bit string is stored in a different sector of the block. When each block is made up of 12 sectors, for instance, if the block number is denoted as b0b1b2b3b4b5, the positional information bit string may be expressed as 00001b0b1b21b3b4b5, where the first 5 bits “00001” constitute an identification code.

Abstract: A read/write head for use with bit-patterned media detects write synchronization errors between a write clock and the bit-patterned media. In particular, the read/write head writes data to the bit-patterned media using a write clock. The data is then read from the bit-patterned media and used to detect write synchronization errors between the write clock and the location of bit-islands on the bit-patterned media. Based on detected write synchronization errors, the phase associated with the write clock is modified to align the write clock with the location of bit-islands on the bit-patterned media.

Abstract: The present invention provides a technique for detecting a defect in a tape medium within a relatively short or narrow range. A tape defect detection device includes: a read unit for reading data from a tape medium; an error correction unit for performing error corrections for the data read by the read unit; a correction number counting unit for counting the number of the error corrections, made by the error correction unit, for each of multiple divided areas of the tape medium; a temporary storage unit for temporarily storing, for each of the areas, the number of the error corrections counted by the correction number counting unit; and a detection unit for detecting a defect in the tape medium, on the basis of a distribution of divided areas each having a larger number of error corrections than other divided areas on the tape medium.

Abstract: An information storage apparatus that records servo information and user data on a recording face of a recording medium wherein a track density measuring unit measures the optimal track density for a recording face corresponding to each head targeting a storage medium on which the servo information has not yet been recorded and a recording density measuring unit measures the optimal linear density for each recording face. A servo frame writing unit writes the servo information varying a track pitch to a track pitch corresponding to the optimal track density measured by the track density measuring unit and a recording frequency to a recording frequency corresponding to the optimal linear density measured by the linear density measuring unit, for each head.

Abstract: According to one embodiment, a disk drive that effectively corrects data errors, which are changes in the total number of data bits at the time of reproducing the data. The disk drive has a disk and a disk controller. The disk has a data-recording area constituted by a set of magnetic dots that are physically separated from one another. The disk controller uses error-correcting codes, determining an error that shows a change in the total number of bits in a data-bit string of the data set reproduced.

Abstract: A method for automatically characterizing non-linearities of a perpendicular read-back signal of a recording system is disclosed. The method includes using dibit extraction to obtain a read-back signal having a main pulse and a plurality of echoes where the read-back signal exhibits a baseline shift. An area under the first echo is integrated to obtain a first area where the integrating subtracts any baseline shift area within the first echo and where the first echo is associated with a first non-linearity. The method integrates an area of the read-back signal under the main pulse to obtain a second area where the integrating subtracts any baseline shift area within the main pulse. A first parameter is computed that characterizes the first non-linearity based on the first area and the second area. The method may be applied to characterize several non-linearities.

Abstract: A method for recording data freshness degrees by a tape drive is disclosed. During the recording of a set of data and a data freshness degree associated with the set of data a tape recording medium, a determination is made as to whether or not a fault occurs during the recording. In response to a determination that a fault occurs during the recording, a data freshness degree of data within a faulty portion on the tape recording medium is obtained. The data freshness degree of the set of data is then immediately recorded before the faulty portion on the tape recording medium. The data freshness degree is higher than the data freshness degree of data within the faulty portion.

Abstract: Described herein are media drives for writing information to a media (e.g., a tape media), systems for storing information on a storage medium, and methods of writing information to a media. The devices, systems and methods described herein are error tolerant in that they may permit only a limited number (or arrangement) of bad blocks in an envelope to be written before they erase at least a portion of the envelope that has already been written, and move to a different region of the storage media and re-write the envelope.

Abstract: Provided is a method and apparatus for adaptively controlling the timing of servo pulses in a disk drive in consideration of the amount of spindle jitter generated when a disk rotation speed is changed. The method of controlling the timing of a sector pulse for write operation includes: measuring a spindle jitter value in a data write mode; generating a timing correction value of a sector pulse, which indicates a position of a sector where data is written, according to the measured spindle jitter value; and generating a sector pulse by reflecting the timing correction value of the sector pulse.

Abstract: A disk drive is disclosed comprising a plurality of disk surfaces, including first and second disk surfaces. A first physical zone on a first disk surface has a physical zone boundary at a first predetermined radial location, wherein the first predetermined radial location is different from any of the radial locations of the physical zone boundaries on a second disk surface. A plurality of logical zones are identified having logical zone boundaries defined relative to the physical zone boundaries of at least the first and second disk surfaces, wherein the number of logical zones is greater than the number of physical zones for at least one of the disk surfaces. The logical zones are used to find one of the data sectors corresponding to a block address received from a host.

Abstract: A method and apparatus is disclosed for adjusting the track density by changing the slope of spiral tracks used to servo write a disk drive. A target track density is established for a disk surface, and a plurality of spiral tracks are written to the disk surface in response to the target track density. Each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark, and a slope of the spiral tracks is selected in response to the target track density. The head internal to the disk drive is used to read the spiral tracks in order to write product servo sectors to the disk to define a plurality of data tracks, wherein the slope of the spiral tracks determines the density of the data tracks.

Abstract: A data recording/recovery device (20) comprises a packet generator (34) for including recordable information into a packet (44), the packet initially having a nominal run length limited (RLL) sequence if it were RLL encoded. A randomizer (38) uses a randomizer input value (50) to obtain a modified packet (46) which, when encoded, will at least partially have a different run length limited sequence than the nominal run length limited sequence. A write channel (40) records the modified packet (46) as a track packet at a destination physical location (42) on a storage medium (22). The randomizer input value (50) used to obtain the modified packet (46) is related to a predetermined physical location on the storage medium. In one example embodiment the randomizer input value is related to the destination physical location on the storage medium.

Abstract: A recording and playback apparatus includes a recording and playback unit recording a signal on a storage medium and playing back the signal recorded on the storage medium, the recording and playback unit at least having a magnetic head; a temperature detector detecting a temperature; and a controller executing a test writing controlling process of controlling the recording and playback unit so that a test writing operation on the storage medium is executed according to a result of temperature detection by the temperature detector, executing a checking process of checking whether a signal has been correctly written by the test writing operation, and executing a recording controlling process of controlling a recording operation on the storage medium by the recording and playback unit according to a result of the checking in the checking process.

Abstract: Joint decoding of ISI (Inter-Symbol Interference) channel and modulation codes. A means is presented by which a single, combined ISI and modulation decoding module is operable to process a signal received from an ISI communication channel and directly to generate a soft estimate of information encoded therein. A single module, that employs a decoding transfer function that is substantially matched to the communication channel that introduces the ISI and the modulation encoding performed on the information before being launched into the ISI communication channel. This means is adaptable to a variety of modulation coding systems that are tailored to deal with communication systems that introduce ISI. Moreover, this means is extendable to communication systems employing an error correction code (ECC) such as Reed-Solomon (RS) coding as well as ECCs of an iterative nature such as LDPC (Low Density Parity Check) coding, turbo coding, and/or turbo trellis code modulation (TTCM) coding.

Abstract: Certifying a storage media while servowriting the media by formatting a full compliment of servo data in storage tracks of the media in a minimum number of passes per storage track while simultaneously performing a 100% media certification of the storage tracks during the minimum number of passes per storage track.

Abstract: Embodiments of the invention prevent offtrack write that will be caused due to a head vibration in a storage device. In one embodiment, a hard disk drive (HDD) judges approval/disapproval of write of user data to a magnetic disk by using a read signal for user data in addition to servo data in write processing. Thus, a head vibration which cannot be precisely detected based on servo data is detected to prevent off-track write. More specifically, the HDD acquires a read back signal amplitude of a read element with respect to a user data sector within adjacent servo data during a write access phase, and detects a vibration from a maximum value MAX and a minimum value MIN of the read back signal amplitude to judge data write approval/disapproval.

Abstract: A read channel includes a variable gain amplifier, a low-pass filter, an AGC, an analog-to-digital converter, a frequency synthesizer, a filter, a soft-output detector, an LDPC decoding unit, a synchronizing signal detector, a run-length limited decoding unit, a descrambler, and a first baseline wander corrector. The first baseline wander corrector corrects a baseline variation by a feedforward control.

Abstract: Various systems and methods for accessing data via a variable polarity head assembly are disclosed herein. As one example, a method for accessing data is disclosed that includes receiving a data set, and sampling the data set using positive synchronization to create one data set and negative synchronization to create another data set. A respective sync mark is identified in each of the data sets, and the identified sync marks are compared. Based at least in part on the comparison of the sync marks, a polarity of the data set is identified. Based on the determined polarity of the data set, the data set may be delivered in a known polarity.

Abstract: Method and apparatus for off-track write error recovery. A storage medium is provided with at least first and second tracks, and a write protected status is assigned to the second track to inhibit subsequent writing of data thereto in relation to a position error detected during writing of data to the first track. Preferably, a third track is disposed between the first and second tracks. The position error is preferably characterized as a first position error, and a write fault condition is declared during the writing of data to the first track in relation to a second position error different from the first position error. Data write operations are preferably performed on additional tracks while the write protected status of the second track is maintained. In this way, dual-sided encroachment or other track squeezing effects are reduced.

Abstract: A magnetic recording device comprising a magnetic recording medium, a read-write channel for modulating write data, writing it on the magnetic recording medium, reading data from the magnetic recording medium, and demodulating the read data, and a processor for supplying the write data to the read-write channel and being supplied with the read data from the read-write channel. The processor supplies to the read-write channel a microdefect detection pattern having a first pattern for generating a consecutive magnetization inversion during writing and a second pattern for generating, during reading, a signal having a S/N ratio higher than the signal produced by the first pattern, the read-write channel modulates the microdefect detection pattern, writes it to the magnetic recording medium, reads the microdefect detection pattern, which was written, from the magnetic recording medium, and conducts abnormality detection of the microdefect detection pattern, which was read out.

Abstract: Embodiments of the present invention provide an inspection method for detecting a physical defect of a magnetic disk with high sensitivity without increasing the length of inspection time. In a magnetic disk drive according to one embodiment, the assembling of which has been completed, by reading inspection data written to a magnetic disk, a defect of the magnetic disk is detected in a state in which a read error occurs. Redundant bits of an ECC are added to the inspection data. If a head corresponding to a recording surface to be inspected has superior read performance, an ECC 2 is applied. If the head in question has inferior read performance, an ECC 4 is applied. Accordingly, as compared with a case where a single ECC is applied, the defect detectivity is further improved without increasing the length of inspection time.

Abstract: An apparatus is provided that can detect error locations in certify testing of a magnetic recording medium without influence from undulation of the substrate or irregularities in film thickness distribution of magnetic film of the magnetic recording medium. Such an apparatus tests playback signals of a magnetic recording medium, the magnetic head 53 conducts playback of signals which are recorded in the magnetic recording medium. The AGC unit 34 amplifies the played back signals at a gain rate controlled according to elapsed time after input of a signal originating in an error area of the magnetic recording medium among the played back signals. The CMP unit 38 compares the slice level and the level of the amplified signals, and discriminates the existence or non-existence of error.

Abstract: A recording-medium controlling apparatus that performs a read-access and a write-access of a recording medium in response to access request from a higher-level apparatus, detects a read error that occurs at a time of the read access, and performs a replacement processing, includes an error detecting unit that tries a plurality of the read accesses to an error location on the recording medium to detect whether the read error recurs a plurality of times; and a replacement processing unit that performs, when the error detecting unit detects that the read error recurs a plurality of times, a replacement processing for the error location.

Abstract: A magnetic recording device write channel includes a write equalization encoder for generating a write equalization level signal and a digital to analog converter for converting the write data signal to analog signals for recording. The write equalization level signal from the write equalization encoding device controls an impedance value at an output of said digital-to-analog converter. The output of the digital-to-analog converter is connected to an input of the data transmission line which transmits the write data signal to a write head of the magnetic recording device. Variation in the output impedance of the digital-to-analog converter by comparison to the input impedance of the transmission line controls the level of the equalization transmitted to the write head of the magnetic recording device.

Abstract: A recording medium for storing start position information for each zone, a method of managing data using the information, and an apparatus for recording the information and controlling recording and reproduction of data based on the recorded information. In a disc having a plurality of zones which form a group, and a spare area which is allocated at the start portion or the end portion of the group for replacing defects, when start logical sector numbers of each zone are changed by slipping replacement during initialization or reinitialization, the information is stored in the defect management area to thereby increase the compatibility of the medium. In particular, by the method and apparatus of managing data using information stored in a defect management area, generation of errors is prevented in reading or writing due to the change of a physical position of a real-recorded file which are caused by wrong calculation of the start logical sector numbers for each zone.

Abstract: Prior to recording, a difference between a disc's temporal, maximum recordable length and a temporal length having been consumed by recording data is calculated. A scale is determined to allow a length of a period of a preprogrammed recording to be relatively matched on a timebase bar with the obtained difference's temporal length. Relative to the length of the period of the preprogrammed recording, an amount indicating a shortage of the difference's temporal length is calculated. An image of the timebase bar is created and the determined scale is used to create on the bar an image indicating the calculated amount of shortage, and these images are integrally displayed. Furthermore, if the current recording location and time shift reproduction location are also obtained, these locations are displayed on the same timebase bar.

Abstract: On writing information to an information recording medium including multiple recording areas having logical addresses assigned thereto, each of the recording areas having information recorded therein with a check code generated based on the logical address of the recording area added thereto, the logical address is converted to a physical location of the recording area on the information recording medium, the information recorded in the recording area at that location is read and it is checked whether or not there is a match between the check code added to the information and the logical address so as to write the information only in the case where it is confirmed that there is a match.

Abstract: The present invention relates to a decoding apparatus and method, a program storage medium, and a program, which allow high-performance decoding of a modulation code encoded in accordance with a variable-length table. A 17PP-SISO decoder 181 performs SISO decoding on a signal supplied from a PR-SISO decoder 81 by using a Viterbi decoding algorithm or a BCJR decoding algorithm in accordance with a trellis represented by paths corresponding, in a one-to-one fashion, to overall transitions in an entire encoding process in accordance with an encoding table 201 of a 17PP code. A resultant SISO-decoded signal is supplied to a turbo decoder 84 via a deinterleaver 83. The turbo decoder 84 performs turbo decoding on the signal output from the 17PP-SISO decoder 181. The present invention can be applied to a recording/reproducing apparatus for recording/reproducing a signal on/from a storage medium such as a high-density optical disk.

Abstract: Bit and byte synchronization for sampling and decoding a data string is provided a single data field u. The data string x has pre-pended to it a short string of 1s (ones), followed by u to yield a string y= . . . 1111, u, x. The string is pre-coded by convolution with 1/(1?D2). PRML-sampling of y starts at an initial phase, and vectors are obtained from that string by sampling at pre-selected phases following the initial sampling point. The vectors of y are compared with vectors corresponding to PRML samples of an initial set of bits in u obtained at predetermined phases. The pair of y, u vectors exhibiting the minimum Euclidian distance yields a sampling correction value by which the initial sampling phase is corrected and a new initial sampling point preceding x is determined. Here, bit and byte synchronization have been achieved and sampling of x proceeds at the corrected phase, from the new initial sampling point.

Abstract: In a magnetic tape device, upon receiving a magnetic tape cartridge from an insertion slot, an authentication unit reads data that is stored in an electronic tag and based on the read data, checks validity of the magnetic tape cartridge. A robot conveys only a valid magnetic tape cartridge to a drive.

Abstract: Systems and methods for managing adjacent track interference in a hard drive. Adjacent track interference potential is ascertained in at least one track, and data corruption is averted via scrubbing data in at least one track with ascertained adjacent track interference potential.

Abstract: A medium storage device reads device specific information from a medium to a memory and performs read/write operation to the medium, which allows receiving commands from a host even if a read error of the device specific information occurs. When an error occurs during the device specific information read processing of the medium storage device after power ON, the alternate data stored in the medium is developed so as to recover the power ON error artificially. For this alternate data, the data at factory shipment is saved in a ROM or a system area of a medium in advance, and is developed from here when necessary. Since commands can be received and executed, a disabled startup of the host system can be prevented.

Abstract: The present disclosure is directed to systems and methods of rewriting defective tracks in a data storage device. In a particular embodiment, the method includes writing a servo pattern on a data storage surface having tracks, detecting a defective track, and rewriting information on the defective track. The method also includes failing a test when a number of defective tracks is greater than a threshold. The method also includes rewriting servo bursts.

Abstract: A recording medium for storing start position information for each zone, a method of managing data using the information, and an apparatus for recording the information and controlling recording and reproduction of data based on the recorded information. In a disc having a plurality of zones which form a group, and a spare area which is allocated at the start portion or the end portion of the group for replacing defects, when start logical sector numbers of each zone are changed by slipping replacement during initialization or reinitialization, the information is stored in the defect management area to thereby increase the compatibility of the medium. In particular, by the method and apparatus of managing data using information stored in a defect management area, generation of errors is prevented in reading or writing due to the change of a physical position of a real-recorded file which are caused by wrong calculation of the start logical sector numbers for each zone.

Abstract: A read channel includes a signal receiver that receives a read back signal and a signal detector to detect symbols in the read back signal. The signal detector includes a first detector that generates raw decisions as a function of the read back signal, a post processor that identifies possible defects in the raw decisions, a selector that independently receives the raw decisions and a list of the possible defects from the first detector and the post processor, respectively, and a decoder that generates final decisions based on the raw decisions and the possible defects identified by the post processor. The decoder performs at least one of Reed-Solomon decoding, Bose Chaudhuri Hocquerghen (BCH) decoding and Hamming Decoding.

Abstract: In one exemplary embodiment, a noise signal is introduced into a read-back signal when data is written to a removable data storage medium. While writing the data to the removable data storage medium, a portion of the data written to the removable data storage medium is read from the removable data storage medium. An error rate is determined based on the portion of the data read from the removable data storage medium. A read-back signal is generated corresponding to the portion of the data read from the removable data storage medium, which is used to detect if an error occurred in writing the portion of the data to the removable data storage medium. A noise signal is added to the read-back signal. The noise signal is adjusted based on the determined error rate.

Abstract: A warning against the possible failure is accurately sent from the magnetic disk device to a host device. In one embodiment, error indices per unit time are stored discontinuously/continuously for each magnetic head, and if the new index (partial integral error rate) updated with the stored multiple error indices as the items to be monitored satisfies required conditions, this state is diagnosed as an abnormality or a pseudo-abnormality, and reported to the host device. The partial integral error rate is updated with an increase in the number of sets of error indices. Each time a new set of error indices per unit time are stored, the oldest of the existing error indices to be monitored is discarded and one of the new error indexes is added. In this way, a new partial integral error rate is calculated from the fixed number of new sets of error indices to be monitored.

Abstract: Embodiments of the invention reduce the error rate of a read error that is caused by a spacing interval between a write head and a read head, which are formed on a slider. In one embodiment, a write head writes user data, which is placed at a position, on a magnetic disk when a read head is placed at a target position in accordance with a head spacing interval and yaw angle. DHO adjustment data is written at a second position, which is obtained by subjecting the read head to DHO correction in order to read the user data written at the target position. When the user data is to be read, a processor reads the DHO adjustment data, changes the read head position to the first position, and controls the operation of a magnetic disk drive to read the user data.

Abstract: A method of retrieving data includes caching data stored in allocation units of a memory (102), preferably a harddisk drive system, of which retrieval incurs a performance penalty. An example of this is data in a spare sector (215), located in a spare area (210) on the harddisk platter (200). The cache memory (103) is, however, a precious commodity. The need for memory space may be reduced by only caching data in spare sectors in which data belonging to a file that is to be retrieved is stored. Also the impact of other kinds of causes of performance penalties may be solved in this way, like those caused by soft defects and fragmentation of files.

Abstract: A disk storage device has a plurality of disk faces and a plurality of heads. The disk storage device protects the data on the disk face for a head before the defect of the head occurs. For each head, a table for accumulating the error generation count generated by the operation of a head is provided. And a control unit predicts the defect of one head based on the accumulated error generation count, reads data on the corresponding disk face by the head of which the defect was predicted, and writes the read data to another corresponding disk face by another head. Since the defect of a head can be predicted, the data can be protected in advance.

Abstract: A method and apparatus for optimizing a hard disc drive, in which parameters of the hard disc drive are updated by periodically performing a retry of the hard disc drive when the hard disc drive is in an idle state and using the accumulated results, and a recording medium that stores programs of the method. The method includes periodically calculating parameter values to optimize the operation of the hard disc drive and applying the optimized parameters calculated in the calculation of optimization parameters to the operation of the hard disc drive.

Abstract: Temporary lock-out is provided while programming a group of non-volatile memory cells to more accurately program the memory cells. After successfully verifying that the threshold voltage of a memory cell has reached the level for its intended state, it is possible that the threshold voltage will subsequently decrease to below the verify level during additional iterations of the programming process needed to complete programming of other memory cells of the group. Memory cells are monitored (e.g., after each iteration) to determine if they fall below the verify level after previously verifying that the target threshold voltage has been reached. Cells that pass verification and then subsequently fail verification can be subjected to further programming. For example, the bit line voltage for the memory cell of interest may be set to a moderately high voltage to slow down or reduce the amount of programming accomplished by each subsequent programming pulse.

Abstract: A disk drive includes a rotatable data storage disk, a transducer, an actuator, and a controller. The transducer is configured to read and write data on the disk. The actuator is configured to position the transducer relative to defined portions of the disk. The controller is configured to determine how many times data has been written to the defined portions of the disk. The controller is also configured to refresh data residing at a particular one of the defined portions of the disk when the number of times data has been written to the particular defined portion of the disk satisfies a threshold value.

Abstract: Apparatus using information about the extent of errors in sensed data for performing as a control function at least one of adjusting the position of a magnetic head to improve alignment relative to a track and selecting from two or more data signals a data signal having the least amount of errors is shown. The apparatus uses information about the extent of errors to perform a control function for reproducing the data stored in predetermined storage locations in a storage media. The apparatus positions a transducer for sensing from predetermined storage locations stored data containing at least one constraint. The transducer generates a first signal representative of the data containing at least one constraint stored in the sensed data and any errors introduced into the sensed data during the sensing.