Hewlett-Packard Development Company, L.p.

Hewlett-Packard Development, L.p.

Peter Arthur Walsh

Rafel Jibry

Robert Morling

Jonathan Peter Buckingham

Andrew Hana

Gregory Keith Trezise

Russell Ian Monk

Neil Thomas Hutchon

Christopher Huw Williams

Darren Edward Kent

Data storage and retrieval methods and apparatus are provided for facilitating data de-duplication for serial-access storage media such as tape. During data storage, input data is divided into a succession of chunks and, for each chunk, a corresponding data item is written to the storage media. The data item comprises the chunk data itself where it is the first occurrence of that data, and otherwise comprises a chunk-data identifier identifying that chunk of subject data. To facilitate reconstruction of the original data on read-back from the storage media a cache () is used together with a database (R), stored on the media, that includes for each duplicated chunk, the location of the corresponding chunk of subject data.

Data de-duplication for serial-access storage media

A data read system comprising a read channel for processing a signal, and a diagnostic controller in communication with the read channel. The diagnostic controller is configured to measure at least one metric of the read channel during processing of a signal containing unknown data. The measured metric is then compared against a stored nominal metric and a warning is generated in response to a result of the comparison. In particular, the warning is generated only if the difference between the measured metric and the stored nominal metric exceeds a threshold.

Predictive diagnosis of a data read system

A tape drive apparatus has at least one rotary head for reading/writing a track. The track has a number of fragments and each fragment has an identifier. The tape drive apparatus has a position indicator apparatus for providing a signal that indicates a rotational position of the head. The combination of the signal and the identifier unequivocally identifies a fragment within the fragments of a track. This has the advantage that non-unique identifiers can be used for the fragments of a track.

Tape drive apparatus

A data reader derives a signal on reading a data holding medium. The data reader has processing circuitry to process the signal. The processing circuitry includes a filter having a variable cut-off frequency, a velocity signal generator that produces a signal corresponding to the velocity of the data holding medium, and a processor. The reads the velocity signal and sets the filter cut-off frequency. Calibration data derived during a calibration operation of only the particular data reader determines the filter cut-off frequency for different speeds of the medium during normal read operations of the medium.

Data readers

Encoded data is decoded by a receiver for an analogue input signal that is converted into a digital signal. A detector produces a sequence of data representative of the analogue signal, a decoder for the sequence of data outputs data indicating that a sequence includes an error. An event detector detects an event which substantially alters or destroys the analogue input signal. The decoder outputs data corresponding to the or each sequence resulting from the altered or destroyed analogue input signal indicating that the sequence is incorrect.

Data recovery

Apparatus responsive to a signal derived by a magnetic transducer includes a variable gain amplifier arrangement having an input responsive to the signal and an output terminal. An analog gain control circuit responds to the signal at the output terminal. An analog to digital converter responds to the signal at the output terminal. Circuitry responsive to an output signal of the analog gain control circuit and an output signal of the analog to digital converter causes the gain of the variable gain amplifier to be simultaneously controlled in response to gain control output signals resulting from the output signals of the analog gain control circuit and the analog to digital converter. Both gain control output signals are derived in response to the same instantaneous value of the output signal at the output terminal of the variable gain amplifier arrangement.

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Burnham-On-Sea, United Kingdom

Peter Arthur Walsh