摘要:
During a read-after-write operation on magnetic tape, a first SCO is formed which includes two encoded processed user data units and is one of T SCOs in a first SCO set. The user data units are each one of T user data units in first and second user data unit sets, respectively, within the first SCO set. The first SCO set is written to the magnetic tape and is immediately read. When an error is detected in one of the user data units, a second SCO is formed to include the first user data unit and, only if an error is not detected in a user data unit in the other user data unit set, to not include the other user data unit, the second SCO being one of T SCOs in a second SCO set. Then, the second SCO set is rewritten to a later position on the tape later.
摘要:
Methods and apparatus are provided for modulation coding a stream of binary input data. A 4-ary enumerative encoding algorithm is applied to the input bit-stream to produce a succession of 4-ary output symbols. The 4-ary algorithm is operative to simultaneously encode respective generalized Fibonacci codes in the odd and even interleaves of the input bit-stream. The bits of each successive 4-ary output symbol are then interleaved, producing an output bit-stream which has global and interleaved run-length constraints. Inverting the bits of the 4-ary output symbols produces an output bit-stream with (G, I)-constraints as in the PRML (G, I) codes used in reverse-concatenation modulation systems. Corresponding decoding systems are also provided.
摘要:
Method and apparatus for decoding data in a data storage system. In operation, a detector generates an output bit stream in dependence on a data block received from a storage subsystem of the data storage system. A post processor connected to the detector generates a first error corrected bit stream in dependence on the output bit stream and the data block. An error correction decoder connected to the post processor generates a second error corrected bit stream in dependence on the first error corrected bit stream and also generates a checksum in dependence of the second error corrected bit stream. A feedback path supplies from the error correction decoder to the post processor pinning data indicative of locations of correct bits in the second error corrected bit stream in the event that the checksum is indicative of errors in the second error corrected bit stream and the second error corrected bit stream comprises at least one correct interleave. The post processor regenerates the first error corrected bit stream in dependence on the pinning data received from the error correction decoder.
摘要:
A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called precoding to the modulation encoded bit stream. However, this precoding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before precoding is applied by the precoder. The decoder subsystem operates in the inverse manner.
摘要:
An apparatus, system, and method are disclosed for read back verification of stored data. A file CRC module calculates a first file CRC for a data file. A segmentation module segments the data file into a plurality of data blocks that comprise a copy of the data file. A block CRC module calculates a data block CRC for each data block. An aggregated CRC module calculates a second file CRC from the data block CRCs. In addition, the aggregated CRC module verifies copy of the data file if the second file CRC is substantially equivalent to the first file CRC.
摘要:
An apparatus for providing dynamic equalizer optimization is disclosed. The present invention solves the above-described problems by providing equalizer coefficient updates that converge towards the same solution as the direct method without having to first write a known pattern to the disk or requiring any prior knowledge of the data already written on the disk. The adaptive cosine function may be used to modify only a DFIR tap set, only the j and k parameters of a cosine equalizer or to modify both the tap set for a DFIR filter and the j and k parameters of the cosine equalizer. Another algorithm, such as the LMS algorithm, may be used to modify parameters not modified by the cosine algorithm.
摘要:
Non-uniform modulation encoding techniques are provided to prevent data from containing bit patterns that are prone to errors during read back. Modulation encoding is performed on a data stream to remove error prone bit patterns. Unconstrained data, such as error check parity, that is inserted into the modulated data stream may contain error prone bit patterns. Stricter modulation constraints are enforced on bits that are next to the unconstrained data, than on the remaining bits. By enforcing stricter modulation constraints on these bits, an entire data bit stream can have a desired modulation constraint.
摘要:
A data storage system includes an encoder subsystem comprising an error correction code encoder, a modulation encoder, and a precoder, and a decoder subsystem similarly comprising a detector, an inverse precoder, a channel decoder, and an error correction code decoder. The error correction encoder applies an error correction code to the incoming user bit stream, and the modulation encoder applies so-called modulation or constrained coding to the error correction coded bit stream. The precoder applies so-called precoding to the modulation encoded bit stream. However, this precoding is applied to selected portions of the bit stream only. There can also be a permutation step where the bit sequence is permuted after the modulation encoder before precoding is applied by the precoder. The decoder subsystem operates in the inverse manner.
摘要:
An apparatus for providing data dependent detection in a data read channel is disclosed. Parameters in a read channel are dynamically adjusted according to data dependent noise. For example, a comparison in an add-compare-select (ACS) unit of a Viterbi decoder may be adjusted or offset terms in error event filters may be biased to choose a Viterbi sequence with more transitions or to compensate for polarity dependent noise.
摘要:
In one embodiment, a data storage system includes a write channel for writing data to a storage medium, the write channel configured to utilize a partial reverse concatenated modulation code. The write channel includes logic adapted for encoding data sets using a C2 encoding scheme, logic adapted for adding a header to each subunit of the data sets, logic adapted for encoding the headers of the data sets with a first modulation encoding scheme, logic adapted for encoding data portions of the data sets with a second modulation encoding scheme, logic adapted for encoding portions of the one or more C2-encoded data sets using a C1 encoding scheme, logic adapted for combining the C1-encoded portions with the modulation-encoded headers of the C2-encoded data sets using a multiplexer, and logic adapted for writing the one or more combined C1 - and C2-encoded data sets to data tracks.