Magnetic disk device and control method

Patent metadata

Field	Value
Publication number	US-9583131-B1
Application number	US-201615062598-A
Country	US
Kind code	B1
Filing date	Mar 7, 2016
Priority date	Nov 30, 2015
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

According to one embodiment, there is provided a magnetic disk device including a magnetic disk, a magnetic head, and a controller. The magnetic head is opposite the magnetic disk. The magnetic head includes a first read head and a second read head. The controller determines a track pitch in the vicinity of a first track or a second track adjacent to the first track of the magnetic disk based on first position information and second position information. The first position information depends on a servo signal read by the first read head and corresponds to the first track. The second position information depends on a servo signal read by the second read head and corresponds to the second track.

First claim

What is claimed is:

1. A magnetic disk device comprising:
a magnetic disk;
a magnetic head opposite the magnetic disk and includes a first read head and a second read head; and
a controller that determines a track pitch in a vicinity of a first track or a second track adjacent to the first track of the magnetic disk based on first position information and second position information, the first position information depending on a servo signal read by the first read head and corresponding to the first track, the second position information depending on a servo signal read by the second read head, and corresponding to the second track.

2. The magnetic disk device according to claim 1 , wherein
the controller obtains a difference of the track pitch between the first and second tracks from a distance between the first and second read heads along a cross-track direction based on the first position information and the second position information and determines the track pitch based on the difference and a first threshold.

3. The magnetic disk device according to claim 2 , wherein
the first position information includes a first offset position of the first read head offset from a center of the first track,
the second position information includes a second offset position of the second read head offset from a center of the second track, and
wherein the controller obtains the difference from a difference between the first offset position and the second offset position.

4. The magnetic disk device according to claim 3 , wherein
the first offset position includes an amount by which a position of the first read head is offset from the center of the first track and a direction in which the first read head is offset, and
wherein the second offset position includes an amount by which a position of the second read head is offset from the center of the second track and a direction in which the second read head is offset.

5. The magnetic disk device according to claim 2 , wherein
if the difference exceeds the first threshold, the controller determines that the track pitch is irregular.

6. The magnetic disk device according to claim 5 , wherein
the controller determines track pitches for multiple places in the second track and, if the number of places whose track pitches were determined to be irregular among the multiple places exceeds a second threshold, registers the second track as a not-in-use track.

7. The magnetic disk device according to claim 6 , wherein
the controller selects a third track and a fourth track along a first direction from the first track to the second track along a cross-track direction on the magnetic disk and determines track pitches for multiple places in the fourth track based on third position information corresponding to a servo signal read by the first read head and corresponding to the third track and fourth position information corresponding to a servo signal read by the second read, head and corresponding to the fourth track and, if the number of places whose track pitches were determined to be irregular among the multiple places exceeds the second threshold, registers the fourth track as the not-in-use track.

8. The magnetic disk device according to claim 6 , wherein
the controller selects the second track and a third track along a first direction from the first track to the second track along a cross-track direction on the magnetic disk and determines track pitches for multiple places in the third track based on fifth position information corresponding to a servo signal read by the first read head and corresponding to the second, track and sixth position information corresponding to a servo signal read by the second read head and corresponding to the third track and, if the number of places whose track pitches were determined to be irregular among the multiple places exceeds the second threshold, registers the third track as the not-in-use track.

9. The magnetic disk device according to claim 6 , wherein
if the number of places which were determined to be irregular is less than the second threshold, the controller registers the places which were determined to be irregular as irregular places to avoid accessing in the second track depending on the number of places which were determined to be irregular.

10. The magnetic disk device according to claim 9 , wherein
if the number of places which were determined to be irregular is less than the second threshold and exceeds a third threshold less than the second threshold, the controller registers the places which were determined to be irregular as the irregular places.

11. A control method in a magnetic disk device comprising a magnetic disk and a magnetic head opposite the magnetic disk and includes a first read head and a second read head, the method comprising:
acquiring first position information corresponding to a servo signal read by the first read head and corresponding to a first track of the magnetic disk and second position information corresponding to a servo signal read by the second read head and corresponding to a second track adjacent to the first track; and
determining a track pitch in the vicinity of the first track or the second track based on the first position information and the second position information.

12. The control method according to claim 11 , wherein
the determining includes:

obtaining a difference of the track pitch between the first and second tracks from the distance between the first and second read heads along a cross-track direction based on the first position information and the second, position information; and
determining the track pitch based on the difference and a first threshold.

13. The control method according to claim 12 , wherein
the first position information includes the first offset position of the first read head offset from a center of the first track,
the second position information includes a second offset position of the second read head offset from a center of the second track, and
wherein obtaining the difference includes obtaining the difference from a difference between the first offset position and the second offset position.

14. The control method according to claim 13 , wherein
the first offset position includes an amount by which a position of the first read head is offset from the center of the first track and a direction in which the first read head is offset, and
wherein the second offset position includes an amount by which a position of the second read head is offset from the center of the second track and a direction in which the second read head is offset.

15. The control method according to claim 12 , wherein
the determining includes, if the difference exceeds the first threshold, determining that the track pitch is irregular.

16. The control method according to claim 15 , wherein the determining includes:
determining track pitches for multiple places in the second track; and
if the number of places whose track pitches were determined to be irregular among the multiple places exceeds a second threshold, registering the second track as a not-in-use track.

17. The control method according to claim 16 , further comprising:
selecting a third track and a fourth track along a first direction from the first track to the second track along a cross-track direction on the magnetic disk and acquiring third position information corresponding to a servo signal read by the first read head and corresponding to the third track and fourth position information corresponding to a servo signal read by the second read

Assignees

• Toshiba Kk

Inventors

• Sugiyama Hiroshi

Classifications

• G11B19/048 Primary

  Testing of disk drives, e.g. to detect defects or prevent sudden failure · CPC title

• G11B5/59627

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

• G11B19/041

  Detection or prevention of read or write errors · CPC title

• G11B5/596 Primary

  for track following on disks {(G11B5/5526, G11B5/5552, G11B5/5565, G11B5/5582 take precedence)} · CPC title

• G11B5/5965

  Embedded servo format (G11B5/59655 takes precedence) · CPC title