Error protection of data stored using variable-length headers

Patent metadata

Field	Value
Publication number	US-2016292033-A1
Application number	US-201615154725-A
Country	US
Kind code	A1
Filing date	May 13, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

In one embodiment, a system includes a controller and logic integrated with and/or executable by the controller. The logic is configured to cause data to be written to a first write section of a magnetic medium as a plurality of first codeword sets, and cause at least some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten codeword sets. A length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than either a length of another rewritten row in the same rewritten codeword set and/or a length of at least one row in a codeword set stored to the first write section of the magnetic medium.

First claim

What is claimed is:

1 . A system, comprising:
a controller and logic integrated with and/or executable by the controller, the logic being configured to:
cause data to be written to a first write section of a magnetic medium as a plurality of first codeword sets; and
cause at least some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten codeword sets,
wherein a length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than either: a length of another rewritten row in the same rewritten codeword set, a length of at least one row in a codeword set stored to the first write section of the magnetic medium, or a length of another rewritten row in the same rewritten codeword set and a length of at least one row in a codeword set stored to the first write section of the magnetic medium.

2 . The system as recited in claim 1 , wherein the data is organized into a plurality of logical arrays, each logical array comprising rows and columns of symbols, each row of a logical array comprising four interleaved headerized C1′ codewords (a headerized CWI-4), wherein each first codeword set comprises a CWI-4 set having M concurrently written rows of a logical array having M corresponding first headers, and wherein each rewritten codeword set comprises a rewritten CWI-4 set having M concurrently rewritten rows of one or more logical arrays having M corresponding rewrite headers.

3 . The system as recited in claim 2 , wherein a length of at least one of the rewrite headers is greater than a length of at least one of the first headers.

4 . The system as recited in claim 2 , wherein rewrite headers for each of the rewritten CWI-4s stored to the rewrite section of the magnetic medium comprise more bytes than first headers for each of the headerized CWI-4s stored in the first write section of the magnetic medium.

5 . The system as recited in claim 2 , wherein each of the logical arrays is non-rectangular due to one or more longer rows in each of the logical arrays comprising more bytes than other rows of each of the logical arrays.

6 . The system as recited in claim 5 , wherein a first header of each of the one or more longer rows of each of the logical arrays comprises more bytes than a first header of the other rows of each of the logical arrays.

7 . The system as recited in claim 5 , wherein a C1′ codeword of each of the one or more longer rows of each of the logical arrays comprises more bytes than a C1′ codeword of the other rows of each of the logical arrays.

8 . The system as recited in claim 5 , wherein row parity of the one or more longer rows of each of the logical arrays comprises more bytes than row parity of the other rows of each of the logical arrays.

9 . The system as recited in claim 1 , wherein the logic is further configured to select which groups of interleaved first codewords to rewrite in the rewrite section of the magnetic medium based on errors being detected in one or more groups of interleaved first codewords stored in the first write section of the magnetic medium.

10 . The system as recited in claim 9 , wherein the logic is further configured to detect the errors in the one or more groups of interleaved first codewords stored in the first write section of the magnetic medium using a read-while-write process.

11 . A computer-implemented method, comprising:
causing data to be written to a first write section of a magnetic medium as a plurality of first codeword sets; and causing at least some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten codeword sets, wherein a length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than either: a length of another rewritten row in the same rewritten codeword set, a length of at least one row in a codeword set stored to the first write section of the magnetic medium, or a length of another rewritten row in the same rewritten codeword set and a length of at least one row in a codeword set stored to the first write section of the magnetic medium.

12 . The method as recited in claim 11 , wherein the data is organized into a plurality of logical arrays, each logical array comprising rows and columns of symbols, each row of a logical array comprising four interleaved headerized C1′ codewords (a headerized CWI-4), wherein each first codeword set comprises a CWI-4 set having M concurrently written rows of a logical array having M corresponding first headers, and wherein each rewritten codeword set comprises a rewritten CWI-4 set having M concurrently rewritten rows of one or more logical arrays having M corresponding rewrite headers.

13 . The method as recited in claim 12 , wherein a length of at least one of the rewrite headers is greater than a length of at least one of the first headers.

14 . The method as recited in claim 12 , wherein rewrite headers for each of the rewritten CWI-4s stored to the rewrite section of the magnetic medium comprise more bytes than first headers for each of the headerized CWI-4s stored in the first write section of the magnetic medium.

15 . The method as recited in claim 12 , wherein each of the logical arrays is non-rectangular due to one or more longer rows in each of the logical arrays comprising more bytes than other rows of each of the logical arrays.

16 . The method as recited in claim 15 , wherein a first header of each of the one or more longer rows of each of the logical arrays comprises more bytes than a first header of the other rows of each of the logical arrays.

17 . The method as recited in claim 15 , wherein a C1′ codeword of each of the one or more longer rows of each of the logical arrays comprises more bytes than a C1′ codeword of the other rows of each of the logical arrays, and wherein row parity of the one or more longer rows of each of the logical arrays comprises more bytes than row parity of the other rows of each of the logical arrays.

18 . The method as recited in claim 11 , further comprising:
detecting errors in one or more groups of interleaved first codewords stored in the first write section of the magnetic medium using a read-while-write process; and selecting which groups of interleaved first codewords to rewrite in the rewrite section of the magnetic medium based on the errors detected in the one or more groups of interleaved first codewords stored in the first write section of the magnetic medium.

19 . A computer program product, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the embodied program instructions executable by a processor to cause the processor to perform a method comprising:
causing data to be written to a first write section of a magnetic medium as a plurality of first codeword sets; and causing at least some of the data to be written to a rewrite section of the magnetic medium as one or more rewritten codeword sets, wherein a length of at least one rewritten row stored to the rewrite section of the magnetic medium is greater than either: a length of another rewritten row in the same rewritten codeword set, a length of at least one row in a codeword set stored to the first write section of the magnetic medium, or a length of another rewritten row in the same rewritten codeword set and a length of at least one row in a codeword set stored to the first write sectio

Assignees

• IBM

Inventors

• Cideciyan Roy D
• Furrer Simeon
• Hutchins Robert A
• Tanaka Keisuke

Classifications

• G11B20/1833 Primary

  by adding special lists or symbols to the coded information (G11B20/1806, G11B20/1866 take precedence) · CPC title

• G06F3/0682

  Tape device · CPC title

• G06F3/0619

  in relation to data integrity, e.g. data losses, bit errors · CPC title

• G06F3/064

  Management of blocks · CPC title

• G11B5/00817

  on longitudinal tracks only, e.g. for serpentine format recording · CPC title