Sequential data storage with rewrite using dead-track detection

Patent metadata

Field	Value
Publication number	US-10600443-B2
Application number	US-201916358131-A
Country	US
Kind code	B2
Filing date	Mar 19, 2019
Priority date	Dec 19, 2017
Publication date	Mar 24, 2020
Grant date	Mar 24, 2020

Abstract

A system includes, according to one embodiment, a magnetic head having a plurality of write transducers configured to store data to tracks of a sequential access medium and a plurality of read transducers. Each read transducer is configured to read data from the sequential access medium after being written thereto by a corresponding write transducer. A first of the read transducers is aligned with a first of the write transducers, wherein the output of the first read transducer is produced during read-while-write. The system also includes a controller and logic integrated with and/or executable by the controller. The logic is configured to read, using the plurality of read transducers, encoded data from a plurality of tracks of the sequential access medium simultaneously. The logic is configured to determine that one or more tracks of the sequential access medium are dead within a sliding window and rewrite a set of encoded data from the one or more dead tracks to one or more live tracks in a rewrite area of the sequential access medium. Other systems, methods, and computer program products are described according to more embodiments.

First claim

What is claimed is:

1. A system, comprising:
a magnetic head having a plurality of write transducers configured to store data to tracks of a sequential access medium and a plurality of read transducers, each read transducer being configured to read data from the sequential access medium after being written thereto by a corresponding write transducer, wherein a first of the read transducers is aligned with a first of the write transducers, wherein the output of the first read transducer is produced during read-while-write; and
a controller and logic integrated with and/or executable by the controller, the logic being configured to:
read, using the plurality of read transducers, encoded data from a plurality of tracks of the sequential access medium simultaneously;
determine that one or more tracks of the sequential access medium are dead within a sliding window; and
rewrite a set of encoded data from the one or more dead tracks to one or more live tracks in a rewrite area of the sequential access medium, and

wherein the live tracks comprise all of the plurality of tracks of the sequential access medium except for the one or more dead tracks.

2. The system as recited in claim 1 , wherein the data from the one or more dead tracks is from a first codeword interleave (CWI) set, and wherein the data from the one or more dead tracks is rewritten to a portion of the rewrite area corresponding to the first CWI set.

3. The system as recited in claim 1 , wherein the data from the one or more dead tracks is from a first codeword interleave (CWI) set, and wherein the data from the one or more dead tracks is rewritten to a portion of the rewrite area corresponding to a second CWI set.

4. The system as recited in claim 1 , wherein the logic configured to determine whether the one or more tracks of the sequential access medium are dead is configured to monitor a quality of data written to the sequential access medium, the quality being indicated via an averaged signal-to-noise ratio (SNR) for each individual track during read-while-write within the sliding window.

5. The system as recited in claim 1 , wherein the logic configured to determine whether the one or more tracks of the sequential access medium are dead is configured to monitor a quality of data written to the sequential access medium, the quality being indicated via results of decoding first written codewords for each individual track during read-while-write within the sliding window.

6. The system as recited in claim 1 , wherein the logic configured to determine whether the one or more tracks of the sequential access medium are dead is configured to monitor a quality of data written to the sequential access medium, the quality being indicated via results of performing cyclic redundancy check (CRC) on headers of data from a first codeword interleave (CWI) set for each individual track during read-while-write.

7. The system as recited in claim 1 , wherein the sliding window includes a predetermined number of codeword interleave (CWI) sets being written to the sequential access medium, and wherein the set of encoded data rewritten to the one or more live tracks in the rewrite area of the sequential access medium comprises two CWIs.

8. The system as recited in claim 1 , wherein the logic is configured to decode the encoded data read from the plurality of tracks prior to determining whether any tracks of the sequential access medium are dead within the sliding window.

9. A method, comprising:
reading, using a plurality of read transducers, encoded data from a plurality of tracks of a sequential access medium simultaneously;
determining that a first of the tracks of the sequential access medium is dead within a sliding window in response to a determination that an output from a first read transducer is insufficient; and
rewriting a set of encoded data from the one or more dead tracks to one or more live tracks in a rewrite area of the sequential access medium,
wherein the first read transducer is aligned with a first write transducer configured to store data to the first track, wherein the output of the first read transducer is produced during read-while-write, and wherein the live tracks comprise all of the plurality of tracks of the sequential access medium except for the one or more dead tracks.

10. The method as recited in claim 9 , wherein the first read transducer is aligned with a first write transducer configured to store data to the first track, wherein the output of the first read transducer is produced during read-while-write.

11. The method as recited in claim 9 , wherein the data from the one or more dead tracks is from a first codeword interleave (CWI) set, and wherein the data from the one or more dead tracks is rewritten to a portion of the rewrite area corresponding to the first CWI set.

12. The method as recited in claim 9 , wherein the data from the one or more dead tracks is from a first codeword interleave (CWI) set, and wherein the data from the one or more dead tracks is rewritten to a portion of the rewrite area corresponding to a second CWI set.

13. The method as recited in claim 9 , wherein the determining whether the one or more tracks of the sequential access medium are dead comprises monitoring a quality of data written to the sequential access medium, the quality being indicated via information selected from the group consisting of: an averaged signal-to-noise ratio (SNR) for each individual track during read-while-write within the sliding window, results of decoding first written codewords for each individual track during read-while-write within the sliding window, and results of performing cyclic redundancy check (CRC) on headers of data from a first codeword interleave (CWI) set for each individual track during read-while-write.

14. The method as recited in claim 9 , wherein the sliding window includes a predetermined number of codeword interleave (CWI) sets being written to the sequential access medium, and wherein the set of encoded data rewritten to the one or more live tracks in the rewrite area of the sequential access medium comprises two CWIs.

15. The method as recited in claim 9 , further comprising decoding the encoded data read from the plurality of tracks prior to determining whether any tracks of the sequential access medium are dead within the sliding window.

16. A computer program product, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the embodied program instructions being executable by a processor to cause the processor to:
read, by the processor using a plurality of read transducers, encoded data from a plurality of tracks of a sequential access medium simultaneously;
determine, by the processor, that one or more tracks of the sequential access medium are dead within a sliding window in response to a determination that an output from a read transducer reading each dead track is insufficient; and
rewrite, by the processor, a set of encoded data from the one or more dead tracks to one or more live tracks in a rewrite area of the sequential access medium,
wherein the read transducers are aligned with write transducers configured to store data to the tracks, wherein the output of the read transducers is produced during read-while-write, and wherein the live tracks comprise all of the plurality of tracks of the sequential access medium except for the one or more dead tracks.

17. The computer program product as recited in claim 16 , wherein the embodied program instructions that cause the processor to determine wheth

Assignees

• IBM

Inventors

• Butt Kevin D
• Cideciyan Roy D
• Furrer Simeon
• Lantz Mark A

Classifications

• G11B2020/1843

  using a cyclic redundancy check [CRC] · CPC title

• G11B2020/1869

  Preventing ageing phenomena from causing data loss, e.g. by monitoring the age of record carriers or by recognising wear, and by copying information elsewhere when a record carrier becomes unreliable · CPC title

• G11B20/1809

  by interleaving · CPC title

• G11B20/18

  Error detection or correction; Testing {, e.g. of drop-outs} · CPC title

• G11B20/1866

  by interleaving (G11B20/1809 takes precedence) · CPC title