摘要:
A method for adaptively applying an error-correcting code to a storage device is disclosed. A determination is made that a system is in an idle state of input/output requests. First data symbols are copied into a first location within a buffer. First data symbol errors corrected using a first error-correcting code. Second data symbols including corrected bits are written in a second location on the recording media with a second error-correcting code. An error number for the second data symbols in the second location is determined. If the error number is below a first threshold error number, the first data symbols are deleted. If the error number is above the first threshold error number, the second data symbols are deleted.
摘要:
A method for adaptively applying an error-correcting code to a storage device is disclosed. A determination is made that a system is in an idle state of input/output requests. First data symbols are copied into a first location within a buffer. First data symbol errors corrected using a first error-correcting code. Second data symbols including corrected bits are written in a second location on the recording media with a second error-correcting code. An error number for the second data symbols in the second location is determined. If the error number is below a first threshold error number, the first data symbols are deleted. If the error number is above the first threshold error number, the second data symbols are deleted.
摘要:
Embodiments of the invention relate to storing data in a storage array. An aspect of the invention includes receiving write data. The write data is arranged into “r” rows and “n” columns of pages, with each page including a plurality of sectors. The write data is encoded using a plurality of horizontal and vertical erasure correcting codes on the pages. The encoding allows recovery from up to tr erasures in any one of the r rows, up to tr-1 erasures in any one of the remaining r-1 rows, up to tr-2 erasures in any one of the remaining r-2 rows, and so on, such that the encoding allows recovery from up to t1 erasures in the last remaining row. Encoded write data is output from the encoding. The encoded write data is written as a write stripe across n storage devices in a storage array.
摘要:
Techniques are provided for identifying the servo sectors in a track on a data storage device. A data storage device identifies the servo sectors in a track by reading distributed index bits from multiple servo sectors in a track. The data storage device analyzes only one index bit from each servo sector to identify the index of a track. In some embodiments, the index of a track can be identified after examining the index bits stored in a particular number of consecutive servo sectors, even in the presence of errors. The index bits in each track can have an error tolerance with a minimum Hamming distance greater than one. In other embodiments, a data storage device compares a sliding window of the index bits read from the servo sectors to all possible N-bit vectors that exist within a pattern of the index bits stored on a track.
摘要:
A system corrects errors in a bit stream. The system includes an encoder and a decoder. The encoder encodes the bit stream using a low density parity check code by inserting parity check bits into the bit stream to generate codewords. The decoder decodes the codewords using parity check equations that are based on the low density parity check code. The parity check bits may comprise no more than four percent of the bits in the codewords of the low density parity check code. The low density parity check code can have a minimum separation of at least 7 between any two ones in each row of a parity-check matrix that is based on the low density parity check code. The encoder and the decoder can be defined in hardware using logic circuits that are interconnected to implement a trellis based on the low density parity check code.
摘要:
A detector generates a detected sequence, and a post processor generates probability values that indicate the likelihood of a plurality of error events in the detected sequence. The post processor partitions the values into first and second subsets. The post processor selects a first most likely value from the first subset of the values and a second most likely value from the second subset of the values. The post processor generates a bit reliability based on the first and the second most likely values.
摘要:
Skew-tolerant Gray codes have the property that consecutive code words differ in only one co-ordinate position, and the additional property that, in each consecutive group of three consecutive code words, the first and third code words differ in only two adjacent coordinate positions.
摘要:
A method for operating a disk drive having timing marks (TMs) on the disk that are chosen to reduce the probability of misidentification of a TM in the presence of read errors. The disk drive searches for TMs within a fixed TM search window which extends past the TM on the disk. A TM preferably maximizes the post-shift sliding distance for m post-shifts of the TM pattern, where m corresponds to the TM search window boundary. In this manner, the probability of a misidentification of the TM due to a post-shift having a small distance from the TM pattern is reduced. The TM pattern also provides pre-shift error resistance.
摘要:
A method and apparatus for detecting typing errors of critical fixed series of characters (digits) by using at least one redundant parity digit. The invention detects the most common typing errors that involve both permutations and incorrect striking of adjacent characters during data entry via a keyboard of an electronic apparatus. The method provides warning to the data input operator when incorrect data entry occurs and optionally automatically suspends entry thereof.
摘要:
A timing recovery system encodes data while impressing recognizable patterns thereon, enabling precise timing during subsequent readback operations. An uncoded binary sequence is encoded using an m/n rate block coded sequence, incorporating a unique predetermined binary bit pattern that occurs with a selected level of frequency. The encoded sequence is stored on the recording medium as a series of flux transitions. To read back the stored data, a read head measures the flux transitions stored on the medium and generates a representative analog waveform. A sampler samples the waveform in accordance with a timing scheme provided by a timing circuit. The timing circuit adjusts the timing of the samples to ensure that the analog waveform is sampled at appropriate times to yield the most accurate results. The timing circuit evaluates two consecutive samples to identify samples associated with features of the analog readback waveform that corresponds to the predetermined bit patterns. Identified samples are then compared to determine whether timing of samples should be advanced, retarded, or retained with respect to the analog waveform. After a detector translates samples into an enclosed binary bit stream, a decoder decodes the detector's binary bit stream by revising the original encoding process, recreating the original encoded binary sequence.