Method and apparatus for determining a location of a feature on a storage medium

• US 8,599,666 B2
• Filed: 11/05/2012
• Issued: 12/03/2013
• Est. Priority Date: 01/14/2009
• Status: Expired due to Fees

• Current Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Oberg, Mats
• Primary Examiner(s): Agustin, Peter Vincent
• Application Number:
  US13/669,218
• Publication Number:
  US 20130064060A1
• Time in Patent Office: 393 Days
• Field of Search: None
• US Class Current: 369/53.15
• CPC Class Codes: G11B 20/1883 Methods for assignment of alternate areas for defective areas
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 7/0948 specially adapted for detection and avoidance or compensation of imperfections on the carrier, e.g. dust, scratches, dropouts G11B7/095 takes precedence

Abstract

A change in a property of a signal is detected, the signal having been sensed from a storage medium by a disk drive. A count is determined, the count corresponding to a first location on the storage medium at which the change in the property of the signal sensed from the storage medium is detected. The count is used to predict a second location on the storage medium corresponding to the change in the property of the signal sensed from the storage medium. Relative to the first location on the storage medium, the second location on the storage medium is closer to an actual location of a feature on the storage medium that causes the change in the property of the signal sensed from the storage medium.

Claims

1. A method, comprising:

detecting a change in a property of a signal, the signal having been sensed from a storage medium by a disk drive;

determining a count corresponding to a first location on the storage medium at which the change in the property of the signal sensed from the storage medium is detected; and

using the count to predict a second location on the storage medium corresponding to the change in the property of the signal sensed from the storage medium,

wherein, relative to the first location on the storage medium, the second location on the storage medium is closer to an actual location of a feature on the storage medium that causes the change in the property of the signal sensed from the storage medium.

2. A method according to claim 1, wherein:

the feature that causes the change in the property of the signal sensed from the storage medium is a defect on the storage medium; and

the method further comprises changing a setting of the disk drive based on the second location on the storage medium so as to reduce a number of errors resulting from reading data on the storage medium affected by the defect.

3. A method according to claim 2, wherein detecting the change in the property of the signal is performed during a first attempt to read data on the storage medium affected by the defect;

wherein changing the setting of the disk drive is performed during a second attempt to read the data on the storage medium affected by the defect and before attempting to read additional data on the storage medium.

4. A method according to claim 1, further comprising changing a setting of the disk drive when the signal sensed from the storage medium is sensed from the second location on the storage medium.

5. A method according to claim 4, wherein changing the setting of the disk drive comprises at least one of:

changing a gain applied to the signal sensed from the storage medium, changing a dc offset applied to the signal sensed from the storage medium, disabling timing updates used to sense the signal from the storage medium, or disabling sensor tracking updates used to sense the signal from the storage medium.

6. A method according to claim 4, further comprising returning the disk drive to a normal mode of operation when the signal sensed from the storage medium is no longer affected by the feature of the storage medium that causes the change in the property of the signal.

7. A method according to claim 1, wherein using the count to predict the second location on the storage medium comprises:

adjusting the count corresponding to the first location based on a delay in detecting the change in the property of the signal.

8. A method according to claim 1, wherein:

the second location on the storage medium is on a first track of the storage medium; and

the method further comprises predicting, based on the first location, a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium.

9. A method according to claim 1, wherein:

the second location on the storage medium is on a first track of the storage medium; and

the method further comprises;

determining a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium, and

predicting, based on the first location and the third location, a fourth location on a third track of the storage medium, the fourth location corresponding to the feature on the storage medium.

10. A disk drive, comprising:

one or more devices configured to

detect a change in a property of a signal sensed from a storage medium by the disk drive,

determine a count corresponding to first location on the storage medium at which the change in the property of the signal sensed from the storage medium is detected, and

use the count to predict a second location of a feature of the storage medium that causes the change in the property of the signal sensed from the storage medium.

11. A disk drive according to claim 10, wherein the feature that causes the change in the property of the signal sensed from the storage medium is a defect on the storage medium;

wherein the one or more devices are configured to change a setting of the disk drive based on the predicted second location of the defect so as to reduce a number of errors resulting from reading data on the storage medium affected by the defect.

12. A disk drive according to claim 10, wherein the count indicates a number of periods of a clock between (i) a boundary of a unit of data and (ii) when the change in the property of the signal is detected.

13. A disk drive according to claim 10, wherein the one or more devices are configured to disable an update of at least one parameter used by the disk drive to sense the signal from the storage medium when the signal is sensed from the predicted second location.

14. A disk drive according to claim 10, wherein the one or more devices are configured to control an update of at least one parameter used by the disk drive to sense the signal from the storage medium when the signal is sensed from the predicted second location.

15. A disk drive according to claim 10, wherein the change in the property of the signal sensed from the storage medium is a change in an amplitude of the signal from above a first threshold to below the first threshold;

wherein the one or more devices are configured to cause a gain controller of the disk drive to increase a gain applied to the signal sensed from the storage medium when the signal is sensed from the predicted second location and, after the change in the amplitude of the signal, the amplitude remains above a second threshold.

16. A disk drive according to claim 10, wherein:

the second location on the storage medium is on a first track of the storage medium; and

the one or more devices are configured to predict, based on the first location, a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium.

17. A disk drive according to claim 10, wherein the count is a first count, the change in the property of the signal is a first change, and the location within the unit of data at which the first change is detected is on a first track of the storage medium;

wherein the one or more devices are configured to

detect a second change in the property of the sensed signal when the signal is sensed from a second track of the storage medium, the second change caused by the feature that causes the first change;

determine a second count corresponding to a location on the second track at which the second change is detected; and

use the first count and the second count to predict a location of the feature that causes the first change and the second change on a third track of the storage medium.

18. A disk drive according to claim 10, further comprising a disk controller configured to provide one or more detection settings to the one or more devices;

wherein the one or more devices are configured to detect the change in the property of the signal using the one or more detection settings.

19. A method, comprising:

detecting a change in a property of a signal sensed from a storage medium by a disk drive;

determining a count corresponding to a first location at which the change in the property of the sensed signal is detected relative to a particular angular position on the storage medium;

predicting a second location of a feature of the storage medium that causes the change in the property of the sensed signal based on the count;

wherein, relative to the first location, the second location on the storage medium is closer to an actual location of the feature on the storage medium that causes the change in the property of the sensed signal.

20. A method according to claim 19, wherein the feature that causes the change in the property of the sensed signal is a defect on the storage medium, the method further comprising causing the disk drive to enter a defect mode based on the predicted second location of the defect so as to reduce an amount of time during which the defect causes errors in reading data on the storage medium.

21. A method according to claim 20, wherein causing the disk drive to enter the defect mode based on the predicted second location of the defect comprises increasing a defect detection sensitivity of the disk drive when data is being read from the storage medium at a location in proximity to the predicted second location of the defect.

22. A method according to claim 19, wherein:

the particular angular position on the storage medium corresponds to a count of zero;

the method further comprises resetting a previous count to zero upon detecting that the signal is being sensed from the particular angular position on the storage medium.

23. A method according to claim 19, wherein the count indicates a number of periods of a clock between the particular angular position and the first location at which the change in the property of the sensed signal is detected.

24. A method according to claim 19, further comprising causing a change of at least one parameter used by the disk drive to sense the signal from the storage medium when the signal is sensed from the predicted second location.

25. A method according to claim 19, wherein:

the predicted second location on the storage medium is on a first track of the storage medium; and

the method further comprises predicting, based on the first location, a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium.

26. A method according to claim 19, wherein:

the predicted second location on the storage medium is on a first track of the storage medium; and

the method further comprises;

determining a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium, and

predicting, based on the first location and the third location, a fourth location on a third track of the storage medium, the fourth location corresponding to the feature on the storage medium.

27. A disk drive, comprising:

one or more devices configured to

detect a change in a property of a signal sensed from a storage medium by the disk drive,

determine a count corresponding to a first location at which the change in the property of the sensed signal is detected relative to a particular angular position on the storage medium, and

predict a second location of a feature of the storage medium that causes the change in the property of the sensed signal based on the count,

wherein, relative to the first location, the second location on the storage medium is closer to an actual location of the feature on the storage medium that causes the change in the property of the sensed signal.

28. A disk drive according to claim 27, wherein the feature that causes the change in the property of the sensed signal is a defect on the storage medium;

wherein the one or more devices are configured to increase a defect detection sensitivity when the disk drive reads data on the storage medium at a location in proximity to the predicted second location of the defect prior to an attempt by the disk drive to read data on the storage medium at the predicted second location of the defect.

29. A disk drive according to claim 28, wherein the one or more devices are configured to adjust the location at which the defect detection sensitivity is increased prior to a subsequent attempt by the disk drive to read data on the storage medium at the predicted second location of the defect.

30. A disk drive according to claim 27, wherein:

the predicted second location on the storage medium is on a first track of the storage medium; and

the one or more devices are configured to predict, based on the first location, a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium.

31. A disk drive according to claim 27, wherein:

the predicted second location on the storage medium is on a first track of the storage medium; and

the one or more devices are configured to

determine a third location on a second track of the storage medium, the third location corresponding to the feature on the storage medium, and

predict, based on the first location and the third location, a fourth location on a third track of the storage medium, the fourth location corresponding to the feature on the storage medium.