Hewlett-Packard Company

Hewlett-Packard Development Company, L.p.

Christopher Huw Williams

Jonathan Peter Buckingham

Andrew Hana

Robert Philip Morling

Liqun Chen

Rafel Jibry

Gregory Keith Trezise

Neil Thomas Hutchon

Robert Morling

Peter Arthur Walsh

Richard D Barndt

John P Hardwick

Andrew David Brown

Stephen Paul Langford

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 transfer device for transferring data to a removable data storage item. The data transfer device receives content data to be stored to the removable data storage item, encrypts the content data using an encryption key, and transforms at least one of predetermined reference data and the encryption key. The data transfer device also encrypts the transformed predetermined reference data using the encryption key or encrypts the predetermined reference data using the transformed encryption key, and then stores the encrypted content data and the encrypted transformed/predetermined reference data to the removable data storage item.

Data transfer device

A digital data storage (DDS) system for reading DDS tapes employs a partial response maximum likelihood detection system which utilises redundancy in the 8-10 DC free modulation encoding to reduce low frequency noise. The system incorporates a time-varying trellis decoder which embodies some of the PR1 rules together with the rules regarding the charge state or the digital sum variation (DSV) implicit in 8-10 modulation coding. The decoder operates to reject low frequency noise such as that caused by crosstalk noise between adjacent tracks on the tape. The trellis topography has been considerably simplified by adopting a two step six state trellis which operates on bit pairs and in which the states relate to the current DSV value, and sign of the previous bit.

Data retrieval

An adaptive filter 24 for filtering a signal comprising first streams interspersed with second streams (for example the A and B tracks of a signal retrieved from a tape storage device) comprises respective stores for storing initial filter coefficients for each type of stream. The corresponding coefficients are loaded for the beginning of each stream. The stored coefficients for each stream may be a standard set, or they may be from the adaption process of one or more previous streams of that type. The coefficients may be taken part way through the adaption process, in a minimum error portion of the stream.

Data processing apparatus and methods

An adaptive (FFE) filter 24 adaptively filters a signal and updates a plurality of coefficients stored on capacitors 69 to minimize the error between the filter output at 72 and a set of notional reference values supplied by a reference generator 74. The stored values of one or more coefficients are monitored and if the monitored coefficient or coefficients pass respective thresholds or leave respective ranges, indicating the onset of maladaption a default set of coefficients is forced.

A phase lock loop for recovering a bit clock from a signal containing variations in the bit rate includes mans for resetting the frequency of said phase lock loop to a preset value if the loop loses its lock or if adverse conditions are detected. The loop may be reset if the frequency passes a preset limit or if other apparatus responsive to signal quality or signal to noise ratio detects adverse conditions. In one embodiment the signal is also subjected to automatic gain control and to adaptive filtering, and the frequency may be reset if the A.G.C. and/or the adaptive filter coefficients pass preset thresholds.

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Chepstow, United Kingdom

Christopher Huw Williams