Abstract: A tape drive-implemented method, according to one embodiment, includes: causing a servo reader to move in a first direction over a high-density servo pattern which includes a plurality of high-density servo tracks. Each of the servo tracks includes at least two patterns written at different frequencies to produce different periodic waveforms during readback. Moreover, a readback signal is received from the servo reader as the servo reader moves in the first direction. The readback signal is used to set a gain parameter for each of the respective periodic waveforms. Other systems, methods, and computer program products are described in additional embodiments.

Abstract: A tape drive-implemented method, according to another embodiment, includes: determining a length of a window of a servo pattern to use for calculating a lateral position estimate, determining a number of the windows of the servo pattern to use for calculating a lateral position value, receiving signals corresponding to each of the number of the windows of the servo pattern from a single servo channel, calculating a lateral position estimate for each of the number of the windows of the servo pattern, calculating the lateral position value by using the lateral position estimates, and using the lateral position value to control a tape head actuator. Other systems, methods, and computer program products are described in additional embodiments.

Abstract: A tape drive-implemented method, according to one embodiment, includes: determining a number of lateral position estimates to use for calculating a lateral position value, receiving lateral position estimates from a single servo channel, calculating the lateral position value by using the number of lateral position estimates, and using the lateral position value to control a tape head actuator. Other systems, methods, and computer program products are described in additional embodiments.

Abstract: In one embodiment, a system includes a controller and logic integrated with and/or executable by the controller. The logic is configured to cause data to be written to a first write section of a magnetic medium as a plurality of first codeword sets, and cause at least some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten codeword sets. A length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than either a length of another rewritten row in the same rewritten codeword set and/or a length of at least one row in a codeword set stored to the first write section of the magnetic medium.

Abstract: A tape drive-implemented method, according to one embodiment, includes: causing a servo reader to move laterally in a first direction over a high-density servo pattern on a moving magnetic tape, receiving a readback signal from the servo reader as the servo reader moves laterally in the first direction, using amplitudes of the readback signal to determine a maximum energy value of each of the at least two periodic waveforms, and using the maximum energy values to set a gain parameter for each of the respective periodic waveforms. The first direction is perpendicular to a longitudinal axis of the magnetic tape. Moreover, the high-density servo pattern includes a plurality of high-density servo tracks, the servo tracks including at least two patterns written at different frequencies to produce different periodic waveforms during readback. Other systems, methods, and computer program products are described in additional embodiments.

Abstract: In one embodiment, a method includes reading a plurality of narrow-spread (NS) codewords from M tracks of a magnetic tape medium using a plurality of read elements, the plurality of NS codewords collectively comprising data logically organized as a predetermined number of two-dimensional arrays. Rach two-dimensional array includes a predetermined number of NS codewords positioned orthogonally to a predetermined number of wide-spread (WS) codewords, with a first NS codeword from a first two-dimensional array being read in its entirety from the magnetic tape medium prior to reading a second NS codeword from the first two-dimensional array. The method also includes laterally decoding each NS codeword from the first two-dimensional array read from the M tracks of the magnetic tape medium in succession prior to decoding any WS codewords from the first two-dimensional array. The NS codewords are protected with a stronger encoding than the WS codewords within each two-dimensional array.

Abstract: In one embodiment, a method includes receiving data to store to a magnetic tape medium using a tape drive, the data being organized into a predetermined number of two-dimensional arrays, each two-dimensional array including a plurality of narrow-spread (NS) codewords positioned orthogonally to a plurality of wide-spread (WS) codewords (relative spread referring to space occupied on the magnetic tape medium when written). The method also includes successively writing each of the NS codewords onto a plurality of tracks of the magnetic tape medium using a first number of channels of the tape drive capable of writing data to tape tracks simultaneously. A first NS codeword from a first two-dimensional array is completely written to the magnetic tape medium prior to starting to write a second NS codeword from the first two-dimensional array. Also, the plurality of NS codewords are protected with a stronger encoding than the plurality of WS codewords.

Abstract: A tape drive-implemented method, according to one embodiment, includes: determining a servo band configuration of servo bands on a magnetic tape, using servo readers on a magnetic tape head to read one or more of the servo bands based on the determined servo band configuration, and using information read from the one or more of the servo bands to position the magnetic tape head relative to the magnetic tape. An array of data transducers is positioned along the magnetic tape head, the array extending perpendicular to a direction of travel of the magnetic tape. Moreover, a group of the servo readers is positioned at each end of the array of data transducers, and a distance between each of the immediately adjacent servo readers in each of the groups of servo readers is less than or equal to one third of a prespecified width of each of the servo bands.

Abstract: Calculating path metrics, associated with respective states of an n-state trellis, by accumulating branch metrics in a sequence detector. Each path metric is represented by N bits plus a wrap-around bit for indicating wrap-around of the N-bit value of that path metric.

Abstract: In one embodiment, a method includes receiving data and in an iterative process until decoded data is output or a predetermined number of full iterations have occurred: C1 decoding all first subsets of the data, determining whether to stop decoding the data after the C1 decoding, incrementing a half iteration counter to indicate completion of a half iteration, C2 decoding all second subsets of the data two or more times in each half iteration using two or more C2-decoding methods in response to a determination that a second subset is not decoded successfully using a first C2-decoding method, determining whether to stop decoding the data after the C2 decoding, incrementing the half iteration counter to indicate completion of another half iteration, and outputting the set of decoded data in response to a determination that all subsets of the data are decoded successfully.

Abstract: Sequence detectors and detection methods are provided for detecting symbol values corresponding to a sequence of input samples obtained from an ISI channel. The sequence detector comprises a branch metric unit (BMU) and a path metric unit (PMU). The BMU, which comprises an initial set of pipeline stages, is adapted to calculate, for each input sample, branch metrics for respective possible transitions between states of a trellis. To calculate these branch metrics, the BMU selects hypothesized input values, each dependent on a possible symbol value for the input sample and L>0 previous symbol values corresponding to possible transitions between states of the trellis. The BMU then calculates differences between the input sample and each hypothesized input value. The BMU compares these differences and selects, as the branch metric for each possible transition, an optimum difference in dependence on a predetermined state in a survivor path through the trellis.

Abstract: In one embodiment, an apparatus includes a controller and logic integrated with and/or executable by the controller. The logic is configured to perform track-dependent erasure decoding on encoded data based on detection of one or more time-varying signal quality issues associated with at least one of a plurality of tracks read simultaneously from a data storage medium. In another embodiment, a method includes determining, by a magnetic tape drive, track signal quality reliability for a plurality of tracks read simultaneously from a magnetic tape medium. In addition, the method includes performing, by the magnetic tape drive, track-dependent erasure decoding on encoded data based on detection of one or more time-varying signal quality issues associated with at least one of the plurality of simultaneously-read tracks.

Abstract: In one embodiment, a method includes reading, using a plurality of read sensors of a magnetic head in a read channel of a tape drive, encoded data from a plurality of tracks of a magnetic tape medium simultaneously. Also, the method includes monitoring statistics for the read channel, the statistics monitored for the read channel including exponentially averaged mean squared error (MSE) or signal-to-noise ratio (SNR) for each simultaneously read track. Moreover, the method includes performing track-dependent erasure decoding on the encoded data based on detection of one or more time-varying signal quality issues associated with at least one of the plurality of tracks read simultaneously from the magnetic tape medium. The one or more time-varying signal quality issues are determined based on side information about reliability of detected bytes within C1 codewords of each simultaneously-read track.

Abstract: A method for writing a servo pattern to a magnetic tape medium includes orienting a magnetic flux in opposite directions across gaps in the magnetic tape medium, and moving the magnetic tape medium with its servo band above two gaps in a direction along a longitudinal extension of the magnetic tape medium. The magnetic tape medium includes a servo band along the longitudinal extension of the magnetic tape medium and a servo pattern organized in a servo frame with a first burst having at least two servo stripes, and a second burst having at least two servo stripes. For at least one of the first and second bursts, different stripes within a same burst have opposite magnetic polarities with respect to one another. The method further includes applying a current pulse to the coil, moving the magnetic tape medium, and applying another current pulse to the coil.

Abstract: In one general embodiment, a method includes determining a sampling interval for an interpolator using at least one parameter. The method further includes applying the sampling interval to the interpolator in response to determining the sampling interval. In another general embodiment, an apparatus includes an interpolator and a controller. The controller is configured to determine a sampling interval for the interpolator using at least one parameter. The controller is also configured to apply the sampling interval to the interpolator in response to determining the sampling interval.

Abstract: In one embodiment, a method includes receiving data and in an iterative process until decoded data is output or a predetermined number of full iterations have occurred: C1 decoding all first subsets of the data, determining whether to stop decoding the data after the C1 decoding, incrementing a half iteration counter to indicate completion of a half iteration, C2 decoding all second subsets of the data two or more times in each half iteration using two or more C2-decoding methods in response to a determination that a second subset is not decoded successfully using a first C2-decoding method, determining whether to stop decoding the data after the C2 decoding, incrementing the half iteration counter to indicate completion of another half iteration, and outputting the set of decoded data in response to a determination that all subsets of the data are decoded successfully.

Abstract: In one embodiment, a method includes reading packets of data from M parallel data tracks of a magnetic tape to obtain a plurality of (D+P)-symbol codewords which are logically arranged in nM encoded blocks, each packet including a row of an encoded block, where each encoded block includes an array having rows and columns of code symbols, wherein symbols of each of the (D+P)-symbol codewords are distributed over corresponding rows of the nM encoded blocks, decoding sub-blocks from rows and columns of a plurality of product codewords from the nM encoded blocks, each product codeword including a logical array of code symbols having the rows which include respective row codewords and the columns which include respective column codewords, where each sub-block includes a logical array having rows and columns of data symbols, combining the sub-blocks to form a block of data, and outputting the block of data.

Abstract: A tape head assembly includes a set of data readers configured to simultaneously read data from a set of adjacent data tracks of a tape storage medium, each data track having a width; wherein the width of each data reader of the set along a lateral extension of the tape head assembly is equal to or less than the width of a data track wherein the lateral extension of the tape head assembly is orthogonal to a longitudinal extension of the tape storage medium when arranged in a tape drive containing the tape head assembly spanning at least the set of data tracks during reading; and a servo reader arrangement containing at least one servo reader arranged laterally offset from one of the data readers by less than the width of a data track.

Abstract: In one embodiment, a method for decoding data includes iteratively C1 decoding all first subsets of a set of data two or more times in each half iteration using two or more C1-decoding methods when a first subset is not decoded successfully using a first C1 decoding, determining whether to stop decoding the set of data after the C1 decoding and output results of the C1 decoding, incrementing a half iteration counter to indicate completion of a half iteration in response to decoding not being stopped, C2 decoding all second subsets of the set of data, determining whether to stop decoding the set of data after the C2 decoding and output results of the C2 decoding, incrementing the half iteration counter to indicate completion of another half iteration in response to decoding not being stopped, and outputting decoded data when all subsets of the set of data are decoded successfully.

Abstract: In one embodiment, a system includes a data processing unit configured to read encoded data from a magnetic tape medium. The data processing unit is also configured to decode a plurality of codeword interleaves (CWIs) from the encoded data, each CWI being a row in a sub data set logically organized into a two-dimensional array. The array includes a predetermined number of rows and columns of predetermined lengths. The data processing unit is also configured to determine an address for a first-written CWI without successfully decoding a corresponding codeword interleave designation (CWID) from the encoded data, each CWID specifying an address for a corresponding CWI. Also, each CWID is calculated as a function of a logical track number and a CWI set number.