Disk drive generating map of margin rectangles around defects

1. A disk drive comprising:

a disk comprising a plurality of segments;

a head actuated radially over the disk; and

control circuitry operable to:

identify a cluster of defective segments;

define a margin rectangle of segments around each defective segment in the cluster; and

generate a margin map representing the margin rectangles.

2. The disk drive as recited in claim 1 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of data sectors; and

each segment comprises at least one data sector.

3. The disk drive as recited in claim 1 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of servo sectors; and

each segment comprises at least one servo sector.

4. The disk drive as recited in claim 1 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of servo sectors; and

each segment comprises at least one data wedge representing a recording area between each servo sector.

5. The disk drive as recited in claim 1 , wherein:

the disk comprises a plurality of data tracks;

a first defective segment comprises part of a first data track;

a first margin rectangle comprises at least one segment in a second data track near the first data track toward an outer diameter of the disk; and

the first margin rectangle comprises at least one segment in a third data track near the first data track toward an inner diameter of the disk.

6. The disk drive as recited in claim 5 , wherein the first margin rectangle comprises at least one segment preceding the first defective segment and at least one segment following the first defective segment.

7. The disk drive as recited in claim 6 , wherein the margin map comprises:

a first entry identifying the first data track;

a second entry identifying a first segment in the first data track at a start of the first margin rectangle; and

a third entry identifying a last segment in the first data track at an end of the first margin rectangle.

8. The disk drive as recited in claim 7 , wherein the third entry represents a run length from the first segment.

9. The disk drive as recited in claim 6 , wherein the margin map comprises:

a first entry identifying the first data track;

a second entry identifying a first segment in the first data track at a start the first margin rectangle; and

a third entry identifying a last segment in the first data track at an end of a second margin rectangle that overlaps the first margin rectangle.

10. The disk drive as recited in claim 9 , wherein the margin map comprises:

a fourth entry identifying the second data track;

a fifth entry identifying a first segment in the second data track at a start the first margin rectangle; and

a sixth entry identifying a last segment in the second data track at an end of a third margin rectangle that overlaps the second margin rectangle.

11. A method of operating a disk drive comprising a head actuated over a disk comprising a plurality of segments, the method comprising:

identifying a cluster of defective segments;

defining a margin rectangle of segments around each defective segment in the cluster; and

generating a margin map representing the margin rectangles.

12. The method as recited in claim 11 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of data sectors; and

each segment comprises at least one data sector.

13. The method as recited in claim 11 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of servo sectors; and

each segment comprises at least one servo sector.

14. The method as recited in claim 11 , wherein:

the disk comprises a plurality of data tracks;

each data track comprises a plurality of servo sectors; and

each segment comprises at least one data wedge representing a recording area between each servo sector.

15. The method as recited in claim 11 , wherein:

the disk comprises a plurality of data tracks;

a first defective segment comprises part of a first data track;

a first margin rectangle comprises at least one segment in a second data track near the first data track toward an outer diameter of the disk; and

the first margin rectangle comprises at least one segment in a third data track near the first data track toward an inner diameter of the disk.

16. The method as recited in claim 15 , wherein the first margin rectangle comprises at least one segment preceding the first defective segment and at least one segment following the first defective segment.

17. The method as recited in claim 16 , wherein the margin map comprises:

a first entry identifying the first data track;

a second entry identifying a first segment in the first data track at a start of the first margin rectangle; and

a third entry identifying a last segment in the first data track at an end of the first margin rectangle.

18. The method as recited in claim 17 , wherein the third entry represents a run length from the first segment.

19. The method as recited in claim 16 , wherein the margin map comprises:

a first entry identifying the first data track;

a second entry identifying a first segment in the first data track at a start the first margin rectangle; and

a third entry identifying a last segment in the first data track at an end of a second margin rectangle that overlaps the first margin rectangle.

20. The method as recited in claim 19 , wherein the margin map comprises:

a fourth entry identifying the second data track;

a fifth entry identifying a first segment in the second data track at a start the first margin rectangle; and

a sixth entry identifying a last segment in the second data track at an end of a third margin rectangle that overlaps the second margin rectangle.