Read failover method and apparatus for a data storage system

• US 9,251,856 B1
• Filed: 03/20/2015
• Issued: 02/02/2016
• Est. Priority Date: 05/30/2014
• Status: Active Grant

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Wheelock, David W., Dahandeh, Shafa, Krishnan, Anantha Raman, Anderson, Kent D., Raghunathan, Aravind
• Primary Examiner(s): HINDI, NABIL Z
• Application Number:
  US14/664,730
• Time in Patent Office: 319 Days
• Field of Search: 360/39, 360/31, 360/25, 360/53, 360/55, 360/75
• US Class Current: 1/1
• CPC Class Codes: G11B 19/041 Detection or prevention of read or write errors
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/10018 analog processing for digital recording or reproduction G11B20/10037 - G11B20/10481 take precedence
• CPC Class Codes: G11B 20/18 Error detection or correction; Testing , e.g. of drop-outs
• CPC Class Codes: G11B 2220/2516 Hard disks
• 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 5/02 Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• CPC Class Codes: G11B 5/2652 with more than one gap simultaneously operative with controlled single gap G11B5/245
• CPC Class Codes: G11B 5/397 with a plurality of independent magnetoresistive active read-out elements for respectively transducing from selected components
• CPC Class Codes: G11B 5/4886 relative to rotating disc

Abstract

A reader failover system and method are described for a data storage system. At least two reader systems, including a first reader element and a second reader element, situated on the same head, are employed to read a magnetic storage medium. In an aspect, the head is a two-dimensional magnetic recording (TDMR) head. Control circuitry detects when the first reader system provides less than a predetermined performance or fails, and thereafter causes the second reader system, but not the first reader system, to read the magnetic storage medium. In an aspect, a buffer stores a first reader element signal until the control circuitry detects whether or not the first reader element provides less than a predetermined performance or fails. In an aspect, when a reader element fails, data recovery is performed, and all of, or a majority of, the media continues to be readable, improving the data storage system robustness.

Claims

1. An apparatus for a data storage device comprising:

at least a first reader system and a second reader system to read a magnetic storage medium, wherein the first reader system includes a first reader element, and the second reader system includes a second reader element, and wherein a first head includes both the first reader element and the second reader element;

control circuitry to detect when the first reader system provides less than a predetermined performance or fails, and thereafter to cause the second reader system, but not the first reader system, to read the magnetic storage medium; and

the control circuitry to further detect when a third reader system provides less than the predetermined performance or is nonfunctioning, and thereafter to cause the second reader system, but not the third reader system, to read the magnetic storage medium, wherein the third reader system includes a third reader element, and wherein the first head further includes the third reader element.

2. The apparatus of claim 1, wherein the first head is a two-dimensional magnetic recording (TDMR) head.

3. The apparatus of claim 1, wherein the control circuitry:

sets the data storage device to a data recovery mode when the first reader system provides less than the predetermined performance or fails;

provides an alert when the data storage device is set to the data recovery mode; and

directs the second reader system to recover data from the magnetic storage medium.

4. The apparatus of claim 1, wherein:

when a first reader element signal is created, the first reader system passes the first reader element signal from the first reader element to a first read channel, and from the first read channel to the control circuitry; and

when a second reader element signal is created, the second reader system passes the second reader element signal from the second reader element to a second read channel, and from the second read channel to the control circuitry.

5. The apparatus of claim 1, wherein when a first reader element signal is created, the first reader system passes the first reader element signal from the first reader element to a first preamplifier, to a first analog front end, to a first analog-to-digital converter, to a multiplexer, to a first buffer, to an equalizer, and to a digital back end;

wherein a first read channel includes the first analog front end, the first analog-to-digital converter, the multiplexer, the first buffer, the equalizer, and the digital back end;

wherein when a second reader element signal is created, the second reader system passes the second reader element signal from the second reader element to a second preamplifier, to a second analog front end, to a second analog-to-digital converter, to the multiplexer, to a second buffer, to the equalizer, and to the digital back end; and

wherein a second read channel includes the second analog front end, the second analog-to-digital converter, the multiplexer, the second buffer, the equalizer, and the digital back end.

6. The apparatus of claim 5, wherein the first buffer stores the first reader element signal until the control circuitry detects whether or not the first reader system provides less than the predetermined performance or fails.

7. A method for a data storage device, comprising:

employing at least a first reader system and a second reader system to read a magnetic storage medium, wherein the first reader system includes a first reader element, and the second reader system includes a second reader element, and wherein a first head includes both the first reader element and the second reader element;

detecting when the first reader system provides less than a predetermined performance or fails, and thereafter causing the second reader system, but not the first reader system, to read the magnetic storage medium; and

detecting when a third reader system provides less than the predetermined performance or is nonfunctioning, and thereafter causing the second reader system, but not the third reader system, to read the magnetic storage medium, wherein the third reader system includes a third reader element, and wherein the first head further includes the third reader element.

8. The method of claim 7, further comprising not utilizing a signal from the second reader system by the data storage device until the first reader system provides less than the predetermined performance or fails.

9. The method of claim 7, wherein the first head is a two-dimensional magnetic recording (TDMR) head.

10. The method of claim 7, wherein:

causing the second reader system to read the magnetic storage medium comprises utilizing one portion or more than one portion of the second reader system to read the magnetic storage medium; and

causing the first reader system to not read the magnetic storage medium comprises not utilizing one portion or more than one portion of the first reader system.

11. The method of claim 7, further comprising utilizing a controller to detect when the first reader system provides less than the predetermined performance or fails, and thereafter to cause the second reader system, but not the first reader system, to read the magnetic storage medium.

12. The method of claim 11, wherein:

when a first reader element signal is created, the first reader system passes the first reader element signal from the first reader element to a first read channel, and from the first read channel to the controller; and

when a second reader element signal is created, the second reader system passes the second reader element signal from the second reader element to a second read channel, and from the second read channel to the controller.

13. The method of claim 11, further comprising storing the first reader element signal, utilizing a buffer, until the controller detects whether or not the first reader system provides less than the predetermined performance or fails.

14. The method of claim 7, further comprising setting the data storage device to a data recovery mode when the first reader system provides less than a predetermined performance or fails, providing an alert when the data storage device is set to a data recovery mode, and utilizing the second reader system to recover data.

15. The method of claim 7, further comprising:

detecting that the data storage device is situated in a predetermined environmental condition; and

causing the second reader system, but not the first reader system, to read the magnetic storage medium.

16. A non-transitory machine-readable medium including executable instructions for a data storage device, the instructions comprising code for:

employing at least a first reader system and a second reader system to read a magnetic storage medium, wherein the first reader system includes a first reader element, and the second reader system includes a second reader element, and wherein a first head includes both the first reader element and the second reader element;

detecting when the first reader system provides less than a predetermined performance or fails, and thereafter causing the second reader system, but not the first reader system, to read the magnetic storage medium; and

detecting when a third reader system provides less than the predetermined performance or is nonfunctioning, and thereafter causing the second reader system, but not the third reader system, to read the magnetic storage medium, wherein the third reader system includes a third reader element, and wherein the first head further includes the third reader element.

17. The non-transitory machine-readable medium of claim 16, wherein the first head is a two-dimensional magnetic recording (TDMR) head.

18. The non-transitory machine-readable medium of claim 16, further comprising storing the first reader element signal until detecting whether or not the first reader system provides less than the predetermined performance or fails.

19. The non-transitory machine-readable medium of claim 16, further comprising setting the data storage device to a data recovery mode when the first reader system provides less than a predetermined performance or fails, providing an alert when the data storage device is set to a data recovery mode, and utilizing the second reader system to recover data.

20. A method for a data storage device, comprising:

employing at least two reader systems to read a magnetic storage medium, wherein the at least two reader systems include a first reader system and a second reader system, wherein the first reader system includes a first reader element, and the second reader system includes a second reader element, and wherein a first head includes both the first reader element and the second reader element; and

detecting when the first reader system provides less than a predetermined performance or fails, due to a factor that is independent from concurrent use of the first reader system and the second reader system, and thereafter causing the second reader system, but not the first reader system, to read the magnetic storage medium.

21. The method of claim 20, further comprising setting the data storage device to a data recovery mode when the first reader system provides less than a predetermined performance or fails, providing an alert when the data storage device is set to a data recovery mode, and utilizing the second reader system to recover data.

22. The method of claim 20, further comprising determining whether a portion of the first reader system provides less than a predetermined performance or fails, and utilizing a functioning portion of the first reader system.