Recovering user data from a variably encroached data track

Patent metadata

Field	Value
Publication number	US-9875763-B1
Application number	US-201615332475-A
Country	US
Kind code	B1
Filing date	Oct 24, 2016
Priority date	Oct 24, 2016
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

Method and apparatus for recovering user data from a rotatable data recording medium. In some embodiments, a moveable read element detects at least one uncorrectable read error in user data stored in a data sector arranged along a concentric track. A read retry operation is carried out to recover the user data by radially advancing the moveable read element from a first offset value to a different second offset value with respect to the track in accordance with a trajectory profile while transducing the user data from the data sector. This allows data that are variably overwritten (encroached upon) by different radial amounts from an adjacent track to be recovered.

First claim

What is claimed is:

1. A method comprising:
using a moveable read element to detect at least one uncorrectable read error in user data stored in a data sector arranged along a concentric track at a nominally fixed radius with respect to a rotatable data recording medium; and
performing a read retry operation to recover the user data by radially advancing the moveable read element from a first radial offset value with respect to the nominally fixed radius adjacent the beginning of the data sector to a different second offset value with respect to the nominally fixed radius adjacent an end of the data sector in accordance with a continuous sweep profile while transducing the user data from the data sector so that the read element continuously changes radial position from the first radial offset value to the second radial offset value during the transducing of the user data from the data sector.

2. The method of claim 1 , wherein the read element is radially advanced responsive to a trajectory profile comprising different target offset values for the read element at different locations along the data sector.

3. The method of claim 1 , wherein the read retry operation comprises dividing the data sector into a plurality of successive segments, identifying a different offset value for the read element for each of the plurality of successive segments that provides a desired read back response for the associated segment, deriving a trajectory path that nominally follows the different offset values for each of the plurality of successive segments, and moving the read element along the trajectory path from a first end to a second end of the data sector while reading the user data from the data sector.

4. The method of claim 1 , wherein the read element is moved in a selected linear direction across a width of the data sector.

5. The method of claim 1 , wherein the data track is a first data track and the method further comprises a prior step of writing data to a second data track adjacent the first data track that variably encroaches onto the data sector on the first data track along a length of the data sector, and wherein the read element is radially advanced responsive to said variable encroachment to recover the data from the data sector.

6. The method of claim 1 , wherein the read retry operation comprises applying the first offset value to the read element and obtaining a first readback amplitude response from a first portion of the data sector that exceeds a selected threshold, applying the second offset value to the read element and obtaining a second readback amplitude response from a different, second portion of the data sector that exceeds a selected threshold, wherein the first offset value provides a third readback amplitude response from the second portion of the data sector below the selected threshold and the second offset value provides a fourth readback amplitude from the first portion of the data sector below the selected threshold.

7. The method of claim 1 , wherein the read element is a magneto-resistive (MR) sensor and the medium is a rotatable magnetic recording medium.

8. The method of claim 1 , further comprising using a selected one of a channel quality measurement or a bit error rate (BER) measurement to select the first and second offset values.

9. The method of claim 1 , wherein the read element is continuously swept in a radial direction across the data sector from the first of the data sector to the last of the data sector during the reading of the data therefrom toward a selected one of an innermost diameter (ID) or an outermost diameter (OD) of the medium.

10. The method of claim 1 , wherein the data sector is a first data sector, a second data sector is disposed adjacent the first data sector along the concentric track, and the read retry operation comprises reading user data from the first data sector applying a variable radial offset to the read element and reading user data from the second data sector applying a fixed radial offset to the read element during a single revolution of the medium.

11. The method of claim 1 , further comprising transferring the user data from the data sector recovered during the read retry operation to a host device.

12. The method of claim 1 , wherein the read element is disposed in a moveable data transducer, the data transducer further having a write element, the method further comprising a subsequent step of rewriting the user data recovered from the data sector during the read retry operation to the medium using the write element.

13. A data storage device comprising:
a rotatable data recording medium on which is defined a plurality of concentric tracks, each of the tracks having a plurality of data sectors;
a moveable data transducer having a write element configured to write user data to the data sectors and a read element configured to read the user data from the data sectors; and
a control circuit configured to, responsive to detection of a read error associated with a selected data sector on a selected track, perform a read retry operation to recover the user data from the selected data sector by radially advancing the read element in a single selected radial direction from a first radial offset value with respect to a center of the selected track at a beginning portion of the selected data sector to a different second offset value with respect to the center of the selected track at an end portion of the selected data sector during recovery of the user data from the selected data sector, the read retry operation comprising dividing the selected data sector into a plurality of successive segments, identifying a different offset value for the read element for each of the plurality of successive segments that provides a desired read back response for the associated segment, deriving a trajectory path that nominally follows the different offset values for each of the plurality of successive segments, and moving the read element along the trajectory path from a first end to a second end of the data sector.

14. The data storage device of claim 13 , wherein the medium is a magnetic recording medium and the selected data sector on the selected track is partially encroached by data on an immediately adjacent track at a variable rate along the length of the selected data sector, wherein the radial advancement of the read element by the control circuit follows a contour of said encroachment by the immediately adjacent track.

15. The data storage device of claim 13 , wherein the read element is radially advanced responsive to a trajectory profile comprising different target offset values for the read element at different locations along the data sector.

16. The data storage device of claim 13 , wherein the control circuit is characterized as a servo control circuit configured to position the data transducer adjacent different radial locations on the medium using embedded servo data in spaced apart servo fields, wherein the selected data sector is disposed between an adjacent pair of the servo fields along the selected track.

17. The data storage device of claim 13 , wherein the control circuit uses a selected one of a channel quality measurement or a bit error rate (BER) measurement to select the first and second offset values.

18. The data storage device of claim 13 , wherein the control circuit is further configured to transfer the user data recovered from the selected data sector to a host device, and to direct a rewriting of the user data recovered from the selected data sector to the medium.

19. A

Assignees

• Seagate Technology Llc

Inventors

• Jury Jason C
• Liu Siong
• Christensen Joshua W

Classifications

• G11B2020/183

  wherein at least one additional attempt is made to read or write the data when a first attempt is unsuccessful · CPC title

• G11B5/59627 Primary

  Aligning for runout, eccentricity or offset compensation (G11B5/5534, G11B5/59677, G11B5/59688 take precedence) · CPC title

• G11B5/59694

  System adaptation for working during or after external perturbation, e.g. in the presence of a mechanical oscillation caused by a shock · CPC title

• G11B5/59688

  Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns · CPC title

• G11B20/1816 Primary

  Testing · CPC title