Identifying defective data sectors in a disk drive

1. A method for identifying defective data sectors in a disk drive, the method comprising:

generating a test pattern on a portion of a disk surface;

reading the test pattern on the portion to detect an error and if an error is detected:

associating the error with a physical location on the portion to identify a defective area unsuitable for user data;

assigning a severity category to the defective area;

providing a physical defect list (P-list) for listing each defective area, the P-list having a predetermined P-list limit to restrict a number of P-list entries; and

posting the defective areas having a first severity category to the P-list and if the P-list limit is not exceeded by the first severity category entries after all of the defective areas having the first severity category on the portion are posted to the P-list, then:

posting defective areas having a second severity category to the P-list.

2. The method of claim 1 , wherein the portion in a disk surface is a data sector of a track.

3. The method of claim 1 , wherein the portion in a disk surface is a plurality of data sectors of a track.

4. The method of claim 1 , wherein the portion in a disk surface is a plurality of data sectors of a plurality of tracks.

5. The method of claim 1 , wherein the first severity category corresponds to unrecoverable data sector defects.

6. The method of claim 5 , wherein the disk surface is declared unusable if the first severity category entries posted to the P-list exceed the P-list limit.

7. The method of claim 1 , wherein the P-list limit comprises a predetermined percentage of data sectors of the disk surface.

8. The method of claim 7 , wherein the predetermined percentage is 0.04 percent.

9. The method of claim 7 , wherein the predetermined percentage is in the range of 0.01 to 1 percent.

10. The method of claim 7 , wherein the P-list limit comprises a predetermined number of data sectors of the disk surface.

11. The method of claim 1 , wherein the second severity category corresponds to error correction code (ECC) on-the-fly defects.

12. The method of claim 1 , wherein the second severity category corresponds to scratch-fill defects.

13. The method of claim 1 , wherein the second severity category corresponds to channel margin defects.

14. The method of claim 1 , further comprising:

increasing a disk drive reliability factor by a predetermined value if the P-list limit is not exceeded by the first severity category entries.

15. The method of claim 1 , further comprising:

posting defective areas having a third severity category to the P-list if the P-list limit is not exceeded by the second severity category entries.

16. The method of claim 15 , wherein the third severity category corresponds to error correction code (ECC) on-the-fly defects.

17. The method of claim 15 , wherein the third severity category corresponds to scratch-fill defects.

18. The method of claim 15 , wherein the third severity category corresponds to channel margin defects.

19. The method of claim 15 , further comprising:

increasing a disk drive reliability factor by a predetermined value if the P-list limit is not exceeded by the third severity category entries.

20. The method of claim 15 , further comprising:

posting defective areas having a fourth severity category to the P-list if the P-list limit is not exceeded by the third severity category entries.

21. The method of claim 20 , wherein the fourth severity category corresponds to error correction code (ECC) on-the-fly defects.

22. The method of claim 20 , wherein the fourth severity category corresponds to scratch-fill defects.

23. The method of claim 20 , wherein the fourth severity category corresponds to channel margin defects.

24. The method of claim 20 , further comprising:

increasing the disk drive reliability factor by a predetermined value if the P-list limit is not exceeded by the fourth severity category entries.