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: In one embodiment, a method includes computing more than one skew estimate within each timing-based servo (TBS) frame. Each skew estimate is related to an estimated position of a magnetic tape read head in relation to a magnetic tape medium. In another embodiment, a system includes a hardware processor and logic integrated with and/or executable by the hardware processor. The logic is configured to cause the hardware processor to compute an initial skew estimate based on longitudinal position (LPOS) sync-pattern detection flags detected using servo channels which process at least two readback signals, with the proviso that the LPOS sync-pattern detection flags are only used to compute the initial skew estimate. The logic is also configured to compute more than one skew estimate within each TBS frame thereafter, each skew estimate being related to an estimated position of a magnetic tape read head in relation to a magnetic tape medium.

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 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.

Abstract: In one embodiment, a method includes computing more than one skew estimate within each timing-based servo (TBS) frame. Each skew estimate is related to an estimated position of a magnetic tape read head in relation to a magnetic tape medium. In another embodiment, a system includes a hardware processor and logic integrated with and/or executable by the hardware processor. The logic is configured to cause the hardware processor to compute an initial skew estimate based on longitudinal position (LPOS) sync-pattern detection flags detected using servo channels which process at least two readback signals, with the proviso that the LPOS sync-pattern detection flags are only used to compute the initial skew estimate. The logic is also configured to compute more than one skew estimate within each TBS frame thereafter, each skew estimate being related to an estimated position of a magnetic tape read head in relation to a magnetic tape medium.

Abstract: An apparatus includes a loop filter that receives a plurality of input signals. Each of the input signals is based on a different timing error detector output signal. The apparatus also includes a plurality of read channels, a plurality of interpolation filters, and an array of transducers. Each of the interpolation filters is in communication with a corresponding one of the read channels. Each of the transducers is in communication with a corresponding one of the read channels. The loop filter processes the plurality of input signals, and outputs a different total phase signal for each received input signal. Each of the interpolation filters samples the corresponding read channel based on one of the total phase signals output by the loop filter. The loop filter processes the plurality of input signals by calculating a phase estimate of the samples, and a skew estimate of the samples, relative to written data.

Abstract: A block of data is partitioned into a plurality of sub-blocks each including a logical array having rows and columns of data symbols, encoded using a row linear block code and a column linear block code. Each product codeword includes a logical array of code symbols having rows which include respective row codewords and columns which include respective column codewords. The product codewords are encoded by encoding groups of L symbols, using a rate-L/(L+M) linear block code to produce a plurality of (L+M)-symbol codewords which are logically arranged in nQ encoded blocks (where n is an integer greater than zero). Each of the nQ encoded blocks includes an array having rows and columns of code symbols in which each column includes a codeword of the column code.

Abstract: A block of data is partitioned into a plurality of sub-blocks each including a logical array having rows and columns of data symbols, encoded using a row linear block code and a column linear block code. Each product codeword includes a logical array of code symbols having rows which include respective row codewords and columns which include respective column codewords. The product codewords are encoded by encoding groups of L symbols, using a rate-L/(L+M) linear block code to produce a plurality of (L+M)-symbol codewords which are logically arranged in nQ encoded blocks (where n is an integer greater than zero). Each of the nQ encoded blocks includes an array having rows and columns of code symbols in which each column includes a codeword of the column code.

Abstract: In one embodiment, a computer-implemented method includes writing a data set to a first write section of a magnetic medium and rewriting at least some of the data set as rewritten CWI-4 sets to a rewrite section of the magnetic medium. The data set includes a plurality of sub data sets, each sub data set including a data array organized in rows and columns. Each row of the data array includes four interleaved C1 codewords (a CWI-4). A first portion of the data set is stored as CWI-4 sets to the first write section of the magnetic medium with first headers. Each rewritten CWI-4 set is stored to the rewrite section of the magnetic medium as a number of rewritten CWI-4s having corresponding rewrite headers. Also, a length of any one of the rewrite headers is greater than a length of any one of the first headers.

Abstract: A magnetic tape medium includes at least one servo band along a longitudinal extension of the tape medium which at least one servo band comprises servo patterns organized in servo frames for supporting to determine positional information. At least one of the servo frames includes a first burst comprising at least two servo stripes inclined at a first angle with respect to a direction orthogonal to the longitudinal extension of the tape medium, followed by a second burst including at least two servo stripes inclined at a second angle with respect to a direction orthogonal to the longitudinal extension of the tape medium, which second angle is different from the first angle. At least one of the stripes of the first burst has a first magnetic polarity and at least one of the stripes of the second burst has a second magnetic polarity different from the first magnetic polarity.

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 program instructions are executable by a tape drive to cause the tape drive to perform a method. The method includes writing data to a first write section of a magnetic tape, at least some of the data being written in association with first headers. The method also includes selecting some of the data for rewrite based on detected errors. Moreover, the method includes rewriting the selected data to a rewrite section of the magnetic tape, the rewritten data being written in association with rewrite headers. A length of each of the rewrite headers is greater than a length of each of the first headers.

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 method includes loading first data into a first buffer of an interposer during a first time period and loading second data into a second buffer of the interposer and performing a first decoding operation on the first data using a first decoder during a second time period. The method includes loading third data into a third buffer of the interposer, performing the first decoding operation on the second data using the first decoder, and performing a second decoding operation on the first data using a second decoder during a third time period. Moreover, the method includes loading fourth data into a fourth buffer of the interposer, performing the first decoding operation on the third data using the first decoder, and performing the second decoding operation on the second data during a fourth time period. The first and second decoding operations are C1 or C2 decoding operations.

Abstract: Embodiments include methods, systems and computer program products for controlling a lateral position of a tape head of a magnetic tape drive. Aspects include determining a first servo signal by reading position marks from a first servo band on a magnetic tape using a first sensor and determining a second servo signal by reading position marks from a second servo band on the magnetic tape using a second sensor. Aspects also include delaying the first servo signal relative to the second servo signal by a delay and calculating an average signal based on the first and the delayed second servo signal. Aspects further include determining servo information from the average signal indicative of a deviation of the lateral position of the tape head from an ideal lateral position of the tape head and controlling the tape head to adjust its lateral position such that the deviation is decreased.

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 data storage system includes a head configured to produce a signal representing data stored on a storage medium, a bank of noise whitening filters configured to apply one or more noise whitening filters to the signal to produce a filtered signal, and a data-dependent noise mean calculator configured to estimate a data-dependent noise mean from the filtered signal. The system also includes a branch metric calculator configured to perform one or more branch metric calculations on the filtered signal to produce one or more branch metrics, the one or more branch metric calculations accounting for the data-dependent noise mean. Moreover, the system includes an adaptive data-dependent noise-predictive maximum likelihood (D3-NPML) detector configured to generate an output stream from the one or more branch metric calculations.

Abstract: In one embodiment, a tape drive includes a controller including a processor and logic integrated with and/or executable by the processor. The logic is configured to obtain at least two periodic waveform components of a high density (HD) servo signal read by a servo reader from a HD pattern written on a servo band of a magnetic tape medium. The logic is also configured to filter the HD servo signal using a number of digital filters that are configurable to detect waveform components simultaneously read from the magnetic tape medium, each digital filter being configured to match waveform component parameters and tape velocity. Moreover, the logic is configured to compute a position error signal (PES) based on the filtering of the HD servo signal comprising the waveform components.

Abstract: An apparatus includes a loop filter that receives a plurality of input signals. Each of the input signals is based on a different timing error detector output signal. The apparatus also includes a plurality of read channels, a plurality of interpolation filters, and an array of transducers. Each of the interpolation filters is in communication with a corresponding one of the read channels. Each of the transducers is in communication with a corresponding one of the read channels. The loop filter processes the plurality of input signals, and outputs a different total phase signal for each received input signal. Each of the interpolation filters samples the corresponding read channel based on one of the total phase signals output by the loop filter. The loop filter processes the plurality of input signals by calculating a phase estimate of the samples, and a skew estimate of the samples, relative to written data.

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: A method for writing a servo pattern to a magnetic tape medium by a write head is described. The write head includes a coil configured to generate a magnetic flux when applying an electric current thereto, and a pole piece structure configured to guide the generated magnetic flux. The method includes moving the magnetic tape medium with its servo band above the two gaps in a direction along the longitudinal extension of the magnetic tape medium, applying a current pulse to the coil, continuing to move the magnetic tape medium, and applying another current pulse to the coil. The magnetic tape medium includes at least one servo band along the longitudinal extension of the tape medium having servo patterns organized in servo frames for supporting to determine positional information.