Calibrating a defect scan parameter for a disk drive

1. A method of performing a defect scan for a disk drive, the disk drive comprising a disk, and a head actuated over the disk, the method comprising:

(a) recording data on a first data area of the disk substantially free from defects and on a second data area of the disk substantially affected by at least one defect;

(b) initializing a defect scan parameter with an initial setting;

(c) reading the first data area to determine a first defect threshold, and reading the second data area to determine a second defect threshold;

(d) saving a margin representing a difference between the first and second defect thresholds;

(e) adjusting the setting for the defect scan parameter;

(f) repeating (c) and (d) at least once; and

(g) selecting a first setting for the defect scan parameter in response to the margins saved at element (d).

2. The method of performing a defect scan as recited in claim 1 , wherein the first setting selected for the defect scan parameter corresponds to the maximum saved margin.

3. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises a write current of the head.

4. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises a read bias of the head.

5. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises a fly-height of the head.

6. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises a write current overshoot of the head.

7. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises an equalizer parameter for configuring an equalizer circuit.

8. The method of performing a defect scan as recited in claim 1 , wherein the defect scan parameter comprises a gain control parameter for configuring a gain control circuit.

9. The method of performing a defect scan as recited in claim 1 , further comprising copying the first setting for the defect scan parameter to a production disk drive, and performing the defect scan within the production disk drive in response to the first setting.

10. The method of performing a defect scan as recited in claim 1 , further comprising selecting a defect threshold in response to the saved margins.

11. The method of performing a defect scan as recited in claim 10 , further comprising copying the selected defect threshold to a production disk drive, and performing the defect scan within the production disk drive.

12. The method of performing a defect scan as recited in claim 1 , further comprising:

(h) recording data on a third data area of the disk substantially affected by at least one defect;

(i) reading the third data area to determine a third defect threshold;

(j) saving a margin representing a difference between the first and third defect thresholds;

(k) adjusting the setting for the defect scan parameter;

(l) repeating (i) and (j) at least once;

(m) selecting a second setting for the defect scan parameter in response to the margins saved at element (j);

(n) selecting a third setting for the defect scan parameter in response to the first and second settings; and

(o) performing the defect scan in response to the third setting selected for the defect scan parameter.

13. A disk drive comprising:

a disk comprising a first data area substantially free from defects and a second data area substantially affected by at least one defect;

a head actuated over the disk; and

control circuitry operable to:

(a) initialize a defect scan parameter with an initial setting;

(b) read the first data area to determine a first defect threshold, and read the second data area to determine a second defect threshold;

(c) save a margin representing a difference between the first and second defect thresholds;

(d) adjust the setting for the defect scan parameter;

(e) repeat (b) and (c) at least once; and

(f) select a first setting for the defect scan parameter in response to the margins saved at element (c).

14. The disk drive as recited in claim 13 , wherein the first setting selected for the defect scan parameter corresponds to the maximum saved margin.

15. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises a write current of the head.

16. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises a read bias of the head.

17. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises a fly-height of the head.

18. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises a write current overshoot of the head.

19. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises an equalizer parameter for configuring an equalizer circuit.

20. The disk drive as recited in claim 13 , wherein the defect scan parameter comprises a gain control parameter for configuring a gain control circuit.

21. The disk drive as recited in claim 13 , wherein the control circuitry is further operable to select a defect threshold in response to the saved margins.

22. The disk drive as recited in claim 13 , wherein disk further comprises a third data area substantially affected by at least one defect, and the control circuitry is further operable to:

(g) read the third data area to determine a third defect threshold;

(h) save a margin representing a difference between the first and third defect thresholds;

(i) adjust the setting for the defect scan parameter;

(j) repeat (g) and (h) at least once;

(k) select a second setting for the defect scan parameter in response to the margins saved at element (h);

(l) select a third setting for the defect scan parameter in response to the first and second settings; and

(m) perform a defect scan in response to the third setting selected for the defect scan parameter.

23. A disk drive comprising:

a disk comprising a first area substantially free from defects and a second data area substantially affected by at least one defect;

a head actuated over the disk;

a means for sweeping through a plurality of defect scan parameter values and for reading the first and second data areas to determine a plurality of first and second defect thresholds;

a means for determining a plurality of margins representing a difference between the first and second defect thresholds; and

a means for selecting a setting for the defect scan parameter in response to the plurality of margins.