Reconstructive error recovery procedure (ERP) using reserved buffer

Patent metadata

Field	Value
Publication number	US-9564171-B2
Application number	US-201514838317-A
Country	US
Kind code	B2
Filing date	Aug 27, 2015
Priority date	Jan 7, 2014
Publication date	Feb 7, 2017
Grant date	Feb 7, 2017

Abstract

In one embodiment, a tape drive includes a reserved data buffer and logic integrated with and/or executable by a processor. The logic is configured to read a data set from a medium and store a first portion of the data set to the reserved data buffer in response to a determination that the first portion of the data set is correctable using C2 error correction code (ECC). The logic is also configured to replace any stored row of a non-C2-correctable portion of the data set stored to the reserved data buffer with a corresponding row of the data set read from the medium in response to a determination that the stored row of the non-C2-correctable portion of the data set has an equal amount or more C1-correctable error therein than the corresponding row of the data set read from the medium.

First claim

What is claimed is:

1. A tape drive, comprising:
a reserved data buffer and logic integrated with and/or executable by a processor, the logic being configured to:
read a portion of a data set from a medium, the portion of the data set comprising a plurality of rows which form an array;
store the portion of the data set to the reserved data buffer in response to a determination that the portion of the data set is correctable using C2 error correction code (ECC);
replace any stored row of a non-C2-correctable portion of the data set stored to the reserved data buffer with a corresponding row of a portion of the data set read from the medium in response to a determination that the stored row of the non-C2-correctable portion of the data set has an equal amount or more C1-correctable error therein than the corresponding row of the portion of the data set read from the medium; and
replace any stored row of the non-C2-correctable portion of the data set stored to the reserved data buffer with a corresponding C1-correctable row read from the medium in response to a determination that the corresponding C1-correctable row read from the medium has fewer corrected errors therein than the stored row of the non-C2-correctable portion of the data set stored to the reserved data buffer.

2. The tape drive as recited in claim 1 , wherein the logic is configured to compare all rows of the non-C2-correctable portion of the data set stored to the reserved data buffer to corresponding rows of the portion of the data set read from the medium in response to a determination that the rows of the portion of the data set read from the medium are non-C2 correctable prior to replacing rows of the non-C2-correctable portion of the data set stored to the reserved data buffer.

3. The tape drive as recited in claim 1 , wherein the logic is configured to:
aggregate the stored rows of the non-C2-correctable portion of the data set stored to the reserved data buffer to form a portion of the data set stored to the reserved data buffer;
determine whether C2-ECC is capable of correcting all errors in the portion of the data set stored to the reserved data buffer and ensure that no C2-correctable portion of the data set stored to the reserved data buffer is overwritten during subsequent reading of the portion of the data set; and
reread the portion of the data set from the medium using a different setting in an error recovery procedure (ERP) in response to a determination that an error in the portion of the data set stored to the reserved data buffer is not correctable using C2-ECC.

4. The tape drive as recited in claim 3 , wherein during each reread of the portion of the data set, settings are changed in an attempt to better read the portion of the data set from the medium.

5. The tape drive as recited in claim 4 , wherein the logic configured to change settings comprises logic configured to change at least one setting selected from the group comprising: a medium speed during reading, a data flow correction power, channel parameters, and servo tracking.

6. The tape drive as recited in claim 1 , wherein the medium is a magnetic tape.

7. The tape drive as recited in claim 1 , wherein each row comprises a C1-encoded row in an array representing the portion of the data set.

8. The tape drive as recited in claim 1 , wherein the logic is configured to store all of the portion of the data set to the reserved data buffer after a first reading of the portion of the data set from the medium.

9. A method for reading data from a medium, the method comprising:
reading a portion of a data set from a medium, the portion of the data set comprising a plurality of rows which form an array;
storing the portion of the data set to a reserved data buffer in response to a determination that the portion of the data set is correctable using C2 error correction code (ECC);
replacing any stored row of a non-C2-correctable portion of the data set stored to the reserved data buffer with a corresponding row of a portion of the data set read from the medium in response to a determination that the stored row of the non-C2-correctable portion of the data set has an equal amount or more C1-correctable error therein than the corresponding row of the portion of the data set read from the medium; and
replacing any stored row of the non-C2-correctable portion of the data set stored to the reserved data buffer with a corresponding C1-correctable row read from the medium in response to a determination that the corresponding C1-correctable row read from the medium has fewer corrected errors therein than the stored row of the non-C2-correctable portion of the data set stored to the reserved data buffer.

10. The method as recited in claim 9 , comprising comparing all rows of the non-C2-correctable portion of the data set stored to the reserved data buffer to corresponding rows of the portion of the data set read from the medium in response to a determination that the rows of the portion of the data set read from the medium are non-C2 correctable prior to replacing rows of the non-C2-correctable portion of the data set stored to the reserved data buffer.

11. The method as recited in claim 9 , comprising:
aggregating the stored rows of the non-C2-correctable portion of the data set stored to the reserved data buffer to form a portion of the data set stored to the reserved data buffer;
determining whether C2-ECC is capable of correcting all errors in the portion of the data set stored to the reserved data buffer and ensuring that no C2-correctable portion of the data set stored to the reserved data buffer is overwritten during subsequent reading of the portion of the data set; and
rereading the portion of the data set from the medium using a different setting in an error recovery procedure (ERP) in response to a determination that an error in the portion of the data set stored to the reserved data buffer is not correctable using C2-ECC.

12. The method as recited in claim 11 , wherein during each reread of the portion of the data set, settings are changed in an attempt to better read the portion of the data set from the medium.

13. The method as recited in claim 12 , wherein the settings that are changed are selected from the group comprising: a medium speed during reading, a data flow correction power, channel parameters, and servo tracking.

14. The method as recited in claim 9 , comprising storing all of the portion of the data set to the reserved data buffer after a first reading of the portion of the data set from the medium.

15. The method as recited in claim 9 , wherein each row comprises a C1-encoded row in an array representing the portion of the data set.

16. The method as recited in claim 9 , wherein the portion of the data set is reread from the medium and it is determined whether C2-ECC is capable of correcting all errors in the portion of the data set read from the medium prior to processing or the portion of the data set stored to the reserved data buffer after processing thereof until either a corrected portion of the data set is obtained, or a number of allowable retries is reached and the portion of the data set is reported as unreadable.

17. The method as recited in claim 9 , wherein the medium is a magnetic tape.

18. A tape drive, comprising:
a reserved data buffer and logic integrated with and/or executable by a processor, the logic being configured to:
read a data set from a medium;
store a first portion of the data set to the reserved data buffer in response to a determination that the first portion of the data

Assignees

• IBM

Inventors

• Katagiri Takashi
• Nylander-Hill Pamela R
• Tanaka Keisuke

Classifications

• G06F11/1076

  Parity data used in redundant arrays of independent storages, e.g. in RAID systems · CPC title

• G11B20/1833

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

• G11B20/1886 Primary

  with tapes · CPC title

• G11B2020/1853

  using a product code which has inner and outer parity symbols · CPC title

• G11B20/1803

  by redundancy in data representation · CPC title