Method and system for error checking in a bit-patterned media

• US 20090003144A1
• Filed: 06/29/2007
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Erden, Mehmet F., Mallary, Michael L., He, Ching, Chilaka, Venkata S.
• Granted Patent: US 7,835,099 B2
• Time in Patent Office: Days
• US Class Current: 369/30.210
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: G11B 20/1879 Direct read-after-write methods
• CPC Class Codes: G11B 2020/10759 content data
• CPC Class Codes: G11B 2020/10796 address data
• CPC Class Codes: G11B 2020/1836 using a Reed Solomon [RS] code
• CPC Class Codes: G11B 2220/252 Patterned or quantised magnetic media, i.e. bits are stored in predefined single domain elements
• CPC Class Codes: G11B 27/36 Monitoring, i.e. supervising the progress of recording or reproducing for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06
• CPC Class Codes: G11B 5/743 Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks

Abstract

A disc drive system provides increased reliability by detecting and correcting errors associated with bit-patterned media. Write synchronization errors associated with bit-patterned media are addressed by including data storage for temporarily storing data that is being written to the disc drive. The data is read from both the disc drive and the storage medium and compared to detect write synchronization errors. A disc drive system for correcting write synchronization errors includes an encoder, non-volatile storage, and decoder device for implementing a parity-based scheme for increased reliability. Data strings being written to the disc drive are combined in an encoder to generate a parity string. The address of the data being written to the disc drive, along with the updated parity string is stored to the non-volatile storage. The data strings are read from the disc drive by the decoder. If uncorrectable errors are identified, the decoder employs the parity string in conjunction with the other data strings written to the disc drive to reconstruct the data string with uncorrectable errors.

Claims

1. A disc drive system comprising:

a disc drive employing bit-patterned magnetic media for storing user data;

a data storage device connected to store the user data being written to the disc drive;

a data comparator connected to read user data stored to the disc drive and user data stored to the data storage device, wherein the data comparator compares user data stored on the disc drive to the user data stored on the data storage device to identify write synchronization errors in the data stored to the disc drive and stores error data representing both a type of error identified and location corresponding to the identified error.

2. The disc drive system of claim 1, wherein the data storage device comprises a non-volatile storage device.

3. The disc drive system of claim 1, wherein the data comparator identifies insertion, deletion, and substitution errors caused by write synchronization errors.

4. The disc drive system of claim 1, wherein the data comparator stores the type of error detected and the location of the error to the disc drive.

5. The disc drive system of claim 1, wherein the data comparator stores the type of error detected and the location of the error to a track on the disc drives corresponding to the location of the identified error.

6. The disc drive system of claim 1, further including:

an error correction device connected to access the error data wherein the error correction device utilizes the error data to improve error correction of data read from the disc drive.

7. A disc drive system comprising:

a disc drive employing a bit-patterned magnetic media for storing user data;

an encoder that generates a parity string based on data strings written to the disc drive;

a non-volatile storage for storing addresses identifying the location of data strings stored to the disc drive and for storing the parity string generated by the encoder;

a decoder that at a time subsequent to data strings being written to the disc drive reads data strings from the disc drive and determines whether they have uncorrectable errors, wherein if the data string has an uncorrectable error then the parity string and other data strings written to the disc drive are used in conjunction with a decoder algorithm to reconstruct the data string with the uncorrectable error.

8. The disc drive system of claim 7, wherein the decoder accesses the non-volatile storage to retrieve the parity string and an address corresponding to a data string that have not yet been verified.

9. The disc drive system of claim 8, wherein if the data string corresponding to the address retrieved from the non-volatile storage contains no uncorrectable errors, then a decoding algorithm is applied to the data string and the parity string to update the parity string.

10. The disc drive system of claim 9, wherein if the data string corresponding to the address retrieved from the non-volatile storage contains no uncorrectable errors, then the address associated with the data string is removed from the non-volatile storage.

11. The disc drive system of claim 10, wherein the updated parity string is stored to the non-volatile storage.

12. The disc drive system of claim 8, wherein if the data string corresponding to the address retrieved from the non-volatile storage contains uncorrectable errors, then all addresses stored in the non-volatile storage are retrieved from the non-volatile storage and the decoder retrieves all data strings corresponding to the retrieved addresses from the disc drive.

13. The disc drive system of claim 12, wherein the decoder applied a decoding algorithm to the parity string and all data strings retrieved from the disc drive to reconstruct the data string containing uncorrectable errors.

14. The disc drive system of claim 12, wherein the reconstructed data string is rewritten to the disc drive.

15. A disc drive system comprising:

a disc drive employing bit-patterned media;

a bad-bit registry for storing addresses identifying defective bits within the disc drive; and

an error correction device that accesses the bad-bit registry and utilizes the data identifying the location of bad bits to improve error correcting capabilities.

16. The disc drive system of claim 15, wherein the bad-bit registry is stored on the disc drive.

17. The disc drive system of claim 16, wherein the addresses identifying defective bits is stored on a track in which the defective bit is located to reduce the number of address bits required to identify the defective bit.

18. A method of providing error checking for bit-patterned media, the method comprising:

storing user data to a disc drive employing bit-patterned media;

storing user data written to the disc drive to a data storage device;

comparing the user data stored to the disc drive to the user data stored to the data storage device;

identifying write synchronization errors in the data stored to the disc drive; and

storing error data representing both a type of error identified and a location of the identified error;

19. The method of claim 18, wherein storing the error data representing both the type of error identified and the location of the identified error includes storing the identified error to the disc drive

20. The method of claim 18, further including:

utilizing the stored error data to perform error correction on data read from the disc drive.

21. A method of providing error checking for bit-patterned media, the method comprising:

storing user data strings to a disc drive employing bit-patterned media;

applying an encoder algorithm to the user data strings written to the disc drive to generate a parity string;

storing addresses identifying the location of the used data strings stored to the disc drive and the parity string generated by the encoder algorithm to a non-volatile storage;

reading the user data strings stored in the disc drive;

determining whether the user data strings read from the disc drive contain uncorrectable errors; and

reconstructing the user data string by applying a decoder algorithm to the parity string and other data strings stored to the disc drive if the user data string read from the disc drive is determined to have uncorrectable errors.

22. The method of claim 21, further including:

accessing the non-volatile storage to retrieve the parity string and a stored address identifying a user data string stored to the disc drive that has not been read to verify whether the user data string contains uncorrectable errors.

23. The method of claim 22, further including:

applying the decoder algorithm to the user data string and the parity string to generate an updated parity string if no uncorrectable errors are detected in the user data string;

storing the updated parity string to the non-volatile storage; and

erasing the address identifying the user data string verified to have no uncorrectable errors from the non-volatile storage.

24. The method of claim 23, wherein storing the updated parity string to the non-volatile storage includes replacing the previous parity string stored to the non-volatile storage.

25. The method of claim 22, wherein reconstructing the user data string if uncorrectable errors are detected in the user data string includes:

retrieving all addresses stored to non-volatile memory if uncorrectable errors are detected in the user data string;

reading the user data strings identified by the retrieved addresses from the disc drive; and

applying the decoding algorithm to the user data strings and the parity string to reconstruct the user data string having uncorrectable errors.

26. The method of claim 21, further including:

storing the reconstructed data string to the disc drive.