Storage device with adaptive error-correcting code for improved areal efficiency

• US 8,301,948 B2
• Filed: 08/10/2009
• Issued: 10/30/2012
• Est. Priority Date: 08/10/2009
• Status: Active Grant

• Current Assignee: JP Morgan Chase Bank, N.A. (JP Morgan Chase & Co)
• Original Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Inventors: Blaum, Mario, Rubin, Kurt A., Schabes, Manfred E.
• Primary Examiner(s): Merant, Guerrier
• Application Number:
  US12/538,367
• Publication Number:
  US 20110035634A1
• Time in Patent Office: 1,177 Days
• Field of Search: None
• US Class Current: 714/746
• CPC Class Codes: G06F 11/1068 in sector programmable memories, e.g. flash disk G06F11/1072 takes precedence
• 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 2020/10759 content data
• CPC Class Codes: G11B 2020/185 using an low density parity check [LDPC] code
• CPC Class Codes: G11B 2020/1853 using a product code which has inner and outer parity symbols

Abstract

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.

Claims

1. A system comprising:

a recording media capable of storing data;

a processor configured to;

determine that the system is in an idle state of input/output requests;

copy first data symbols from a location of the recording media;

correct the first data symbols using a first error-correcting code;

write second data symbols including the corrected first data symbols to the location on the recording media with a second error-correcting code;

determine an error number for the second data symbols;

compare the error number to a threshold; and

based on the comparison, record the second error-correction code or alternately keep the first error-correction code.

2. The system of claim 1 wherein the first data symbols are written with a weaker error-correcting code and the second data symbols are written with a stronger error-correcting code.

3. The system of claim 1 wherein the first data symbols are written with a stronger error-correcting code and the second data symbols are written with a weaker error-correcting code.

4. The system of claim 1 wherein the recording media is a flash memory.

5. The system of claim 1 wherein the processor is further configured to:

create a desired writing of the first data symbols by encoding the first data based on the first error-correcting code.

6. A method comprising:

determining that a processor is in an idle state of input/output requests;

determining that a first error number for first data written on a recording disk with a strong error-correcting code is above a first threshold error number;

determining a set of bits based on the first data and the strong error-correcting code;

writing the set of bits to the recording disk by applying a first phase shift to a write control signal;

reading second data from the recording disk, the second data being the read written set of bits;

comparing the second data to the set of bits;

determining a second error number for the second data;

comparing the second error number to a second threshold error number; and

based on the comparing;

writing the second data to the recording disk with a first error-correcting code; and

freeing a region of the recording disk storing the strong error-correcting code.

7. The method of claim 6 wherein a timing of a magnetic field generated by a magnetic write head is controlled by the write control signal.

8. The method of claim 6 wherein a timing of the light from a light source used for heating the disk is controlled by the write control signal.

9. The method of claim 6 wherein the first error-correcting code requires less bits than the strong error-correcting code on the recording disk.

10. The method of claim 6 wherein the recording disk is a magnetic hard disk.

11. The method of claim 6 wherein the recording disk is a patterned magnetic hard disk.

12. The method of claim 6 wherein the recording disk is a thermally assisted recording magnetic disk.

13. The method of claim 6 wherein the recording disk is an optical disk.

14. The method of claim 6 further comprising:

creating the desired writing of the first data by encoding the first data based on the strong error-correcting code.

15. The method of claim 6 further comprising:

compacting the first data written on the recording hard disk in response to writing the second data with the first error-correcting code.

16. The method of claim 6 further comprising:

storing information on the recording disk indicating sectors of the recording disk that have been compacted.

17. The method of claim 6 further comprising:

rewriting the set of bits to the recording disk applying a second phase shift to the write control signal;

reading third data from the recording disk, the third data being the read rewritten set of bits; and

comparing the third data to the set of bits.

18. A non-transitory computer readable medium comprising a plurality of instructions to manipulate a processor, the plurality of instructions comprising:

instructions to determine that a processor is in an idle state of input/output requests;

instructions to determine that a first error number for first data written on a magnetic hard disk with a strong error-correcting code is above a first threshold error number;

instructions to determine a set of bits based on the first data and the strong error-correcting code;

instructions to write the set of bits to the recording disk by apply a first phase shift to a write control signal;

instructions to read second data from the recording disk, the second data being the read written set of bits;

instructions to compare the second data to the set of bits;

instructions to determine a second error number for the second data;

instructions to compare the second error number to a second threshold error number; and

instructions to write the second data to the magnetic hard disk with a first weak error-correcting code in response to the comparing.

19. The computer readable medium of claim 18 wherein the first weak error-correcting code requires less bits than the strong error-correcting code on the magnetic hard disk.

20. The computer readable medium of claim 18 wherein the magnetic hard disk is a patterned magnetic hard disk.

21. The computer readable medium of claim 18 further comprising:

instructions to determine an offset margin for the first phase shift; and

instructions to delete the strong error-correcting code data on the magnetic hard disk.

22. The computer readable medium of claim 21 wherein the offset margin is a number of phase shifts that provide a corrected bit in the second data.

23. The computer readable medium of claim 18 further comprising:

instructions to compact the first data written on the magnetic hard disk in response to writing the second data with the weak error-correcting code.

24. The computer readable medium of claim 18 wherein the first phase shift is varied on a bit by bit basis.