Abstract: A computer program product is provided for performing symbol timing recovery in a parallel recording channel system. The computer program product comprises a computer readable storage medium having program instructions embodied therewith. The program instructions are executable by a processor to cause the processor to receive a plurality of timing-error estimates for a plurality of read channels. Each of the timing-error estimates corresponds to one of the read channels. Also, the program instructions are executable by the processor to cause the processor to calculate a common phase based on the plurality of timing-error estimates. Moreover, the program instructions are executable by the processor to cause the processor to calculate a skew of a transducer array based on the plurality of timing-error estimates, and to calculate a different total phase estimate for each read channel based on the calculated common phase and the calculated skew of the transducer array.

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: In one general embodiment, a method includes determining a sampling interval for an interpolator using at least one of: predefined data stored in memory, and a standard deviation of a position error signal. 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 of: predefined data stored in memory, and a standard deviation of a position error signal. 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 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: In one embodiment, a system includes a controller and logic integrated with and/or executable by the controller. The logic is configured to read data stored as a plurality of first codeword sets on a first write section of a magnetic medium. The logic is also configured to read at least some of the data stored as one or more rewritten codeword sets on a rewrite section of the magnetic medium. A length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than: 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: In one embodiment, a method for combination error and erasure decoding for product codes includes receiving, using a hardware processor, captured data. The method also includes generating, using the hardware processor, erasure flags for the captured data and providing the erasure flags to a C2 decoder. Moreover, the method includes setting a stop parameter to be equal to a length of C1 codewords in a codeword interleave used to encode the captured data. In addition, the method includes selectively performing, in an iterative process, error or erasure C1 decoding followed by error or erasure C2 decoding until decoding is successful or unsuccessful. Other methods and computer program products are described in more embodiments.

Abstract: According to one embodiment, a magnetic tape drive includes a controller configured to direct first data through a first finite impulse response (FIR) gain module in response to a determination that the first data is being read from a magnetic tape medium in an asynchronous mode to control FIR gain of the first data. The controller is also configured to direct second data through a second FIR gain module in response to a determination that the second data is being read from the magnetic tape medium in a synchronous mode to control FIR gain of the second data. A FIR gain value of the second FIR gain module is automatically controlled. Other systems for dynamic gain control with adaptive equalizers are described according to more 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 perform iterative decoding on encoded data to obtain decoded data. At least three decoding operations are performed in the iterative decoding, with the decoding operations being selected from a group consisting of: C1 decoding and C2 decoding. The logic is also configured to perform post-decoding error diagnostics on a first portion of the decoded data in response to not obtaining a valid product codeword in the first portion after the iterative decoding of the encoded data. Other systems, methods, and computer program products for producing post-decoding error signatures are presented in accordance with more embodiments.

Abstract: According to one embodiment, a system for processing data includes a processor and logic integrated with and/or executable by the processor. The logic is configured to individually set, for each of one or more range-constrained finite impulse response (FIR) filter taps configured for use in a FIR filter, a predetermined range of values suitable for controlling an equalizer response. The logic is also configured to pass data through the equalizer comprising the FIR filter to obtain equalized data. Each of the one or more range-constrained FIR filter taps are individually adaptive within its predetermined range of values. Also, the data is read from a magnetic storage medium.

Abstract: According to one embodiment, a system for selecting an optimum tape layout to store data on a tape medium includes a processor and logic integrated with and/or executable by the processor, the logic being configured to compute a set of all minimum distances corresponding to a plurality of data set layouts, wherein each minimum distance is computed between a location of a first codeword interleave (CWI) and locations of all other CWIs in a common sub data set (SDS), and calculate a first performance metric associated with each possible set of parameters using the set of all minimum distances for the plurality of data set layouts, the parameters being associated with at least a tape drive and the tape medium. More systems, methods, and computer program products for selecting optimum tape layouts to store data on tape media are described in accordance with other embodiments.

Abstract: In one embodiment, a system includes logic configured to cause data, organized into a plurality of logical arrays including rows and columns of symbols, to be written to a first write section of a magnetic medium as a plurality of CWI-4 sets, each row of the logical arrays including four interleaved headerized C1? codewords (a headerized CWI-4), where each CWI-4 set includes M concurrently written rows of a logical array having M corresponding first headers, and cause some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten CWI-4 sets, where a length of at least one rewritten row is greater than at least one of: a length of another rewritten row in the same rewritten CWI-4 set, and a length of at least one row in a CWI-4 set stored to the first write section of the magnetic medium.

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: According to one embodiment, a system for processing data includes a processor and logic integrated with and/or executable by the processor, the logic being configured to individually set, for each of one or more range-constrained finite impulse response (FIR) filter taps configured for use in a FIR filter, a predetermined range of values suitable for controlling an equalizer response, and pass data through the equalizer including the FIR filter to obtain equalized data, wherein each of the one or more range-constrained FIR filter taps are individually adaptive within its predetermined range of values. Other systems and methods for processing data by constraining FIR filter taps while reading data from a data storage medium are described in more embodiments.

Abstract: In one embodiment, a system for processing data includes an equalizer having a finite impulse response (FIR) filter configured to process data read with a channel using servo coefficients to generate equalized data, and one or more low-pass filters configured to filter the equalized data to output filtered data. The one or more low-pass filters is configured to remove high frequency noise from the equalized data. A method for processing data in a read channel, in one embodiment, includes receiving data read from a magnetic tape using the read channel of a magnetic tape drive. A finite impulse response (FIR) filter is applied to the data by an equalizer using servo coefficients to output equalized data. One or more low-pass filters is applied to the equalized data to obtain filtered data, the one or more low-pass filters being configured to remove high frequency noise from the equalized data.

Abstract: In one embodiment, a tape drive system includes a soft detector having logic configured to execute a first forward loop of a detection algorithm on a first block of signal samples during a first time interval, execute a first reverse loop of the detection algorithm on the first block of signal samples during a second time interval, execute a second reverse loop of the detection algorithm on the first block of signal samples during a fifth time interval, and execute a second forward loop of the detection algorithm on the first block of signal samples during a fourth time interval using second soft information. Other tape drive systems and computer program products for decoding data are presented in more embodiments.

Abstract: According to one embodiment, a magnetic tape drive includes a controller configured to direct first data through a first finite impulse response (FIR) gain module in response to a determination that the first data is being read from a magnetic tape medium in an asynchronous mode to control FIR gain of the first data. The controller is also configured to direct second data through a second FIR gain module in response to a determination that the second data is being read from the magnetic tape medium in a synchronous mode to control FIR gain of the second data. A FIR gain value of the second FIR gain module is automatically controlled. Other systems for dynamic gain control with adaptive equalizers are described according to more embodiments.

Abstract: According to one embodiment, a method for processing data includes directing first data through a first FIR gain module in response to a determination that the first data is being read from a magnetic tape medium in an asynchronous mode to control FIR gain of the first data. The method also includes directing second data through a second FIR gain module in response to a determination that the second data is being read from the magnetic tape medium in a synchronous mode to control FIR gain of the second data. Other systems and methods for processing data using dynamic gain control with adaptive equalizers are presented according to more embodiments.

Abstract: In one embodiment, a method is provided to receive a set of data and in an iterative process: C1 decode all first subsets of the 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 method, determine whether to stop decoding the set of data after the C1 decoding and output results of the C1 decoding, increment a half iteration counter to indicate completion of a half iteration, C2 decode all second subsets of the set of data, determine whether to stop decoding the set of data after the C2 decoding and output results of the C2 decoding, increment the half iteration counter to indicate completion of another half iteration, and output the set of decoded data when all subsets of the set of data are decoded successfully.

Abstract: In one embodiment, a system for cycle-slip resilient iterative read channel operation includes a processor and logic integrated with and/or executable by the processor. The logic is configured to, in an iterative process until a maximum number of iterations has been reached or a valid codeword is produced, execute cycle-slip detection on signal samples to detect one or more cycle-slip events. Also, the logic is configured to selectively alter a timing estimate driving a phase-locked loop (PLL) during any time interval determined to experience a cycle slip in a first pass as indicated by one or more cycle-slip pointers. Additionally, the logic is configured to generate a set of decisions provided by a detector and generate a set of decisions provided by a decoder. Moreover, the logic is configured to output decoding information relating to the signal samples in response to a decoding algorithm producing a valid codeword.

Abstract: In one embodiment, a computer program product includes a computer readable storage medium having program instructions embodied therewith. The computer readable storage medium is not a transitory signal per se. The embodied program instructions are readable/executable by a processor to cause the processor to write, by the processor, data to a storage medium of a data storage system using a partial reverse concatenated modulation code. The partial reverse concatenated modulation code includes encoding the data by applying a C2 encoding scheme prior to encoding the data by applying one or more modulation encoding schemes, followed by encoding the data by applying a C1 encoding scheme subsequent to the encoding of the data with the one or more modulation encoding schemes. Other computer program products for writing data to a storage medium of a data storage system using a partial reverse concatenated modulation code are presented according to more embodiments.