Disk drive adjusting a defect threshold when scanning for defective sectors
View Patent ↗A disk drive is disclosed including a disk having a plurality of sectors, and a head actuated over the disk. A defect threshold is initialized, and a first sector is read to generate a first read signal. The first read signal is processed to detect a defect in the first sector relative to the defect threshold. After detecting the defect, the defect threshold is adjusted and the first sector is reread to generate a second read signal. The second read signal is processed to detect the defect in the first sector relative to the adjusted defect threshold.
1. A disk drive comprising:
a disk comprising a plurality of sectors;
a head actuated radially over the disk; and
control circuitry operable to:
initialize a defect threshold;
read a first sector to generate a first read signal;
process the first read signal to detect a defect in the first sector relative to the defect threshold;
after the defect is detected, adjust the defect threshold;
reread the first sector to generate a second read signal; and
process the second read signal to verify the defect in the first sector relative to the adjusted defect threshold.
2. The disk drive as recited in claim 1 , wherein the first sector comprises a data sector.
3. The disk drive as recited in claim 1 , wherein the first sector comprises a servo sector.
4. The disk drive as recited in claim 2 , wherein the control circuitry is further operable to map out the data sector after the defect is detected relative to the adjusted defect threshold.
5. The disk drive as recited in claim 1 , wherein the control circuitry is operable to adjust the defect threshold by increasing the defect threshold.
6. The disk drive as recited in claim 1 , wherein the control circuitry is operable to adjust the defect threshold by decreasing the defect threshold.
7. The disk drive as recited in claim 1 , wherein the control circuitry is operable to adjust the defect threshold to decrease the probability that the defect will be detected relative to the adjusted defect threshold.
8. The disk drive as recited in claim 1 , wherein after adjusting the defect threshold the control circuitry is further operable to:
reread the first sector N number of times and track each time the defect is detected relative to the adjusted defect threshold; and
map out a data sector if the defect is detected more than once.
9. The disk drive as recited in claim 8 , wherein the control circuitry is operable to map out the data sector if the defect is detected at least M out of N times, where M is less than N.
10. The disk drive as recited in claim 1 , wherein the control circuitry operable to process the first and second read signals to detect the defect comprises an amplitude detector.
11. The disk drive as recited in claim 1 , wherein the control circuitry operable to process the first and second read signals to detect the defect comprises a digital data detector for detecting an estimated data sequence.
12. The disk drive as recited in claim 1 , wherein the control circuitry operable to process the first and second read signals to detect the defect comprises a servo demodulator operable to demodulate embedded servo sectors written on the disk.
13. A method of operating a disk drive, the disk drive comprising a disk having a plurality of sectors, and a head actuated radially over the disk, the method comprising:
initializing a defect threshold;
reading a first sector to generate a first read signal;
processing the first read signal to detect a defect in the first sector relative to the defect threshold;
after the defect is detected, adjusting the defect threshold;
rereading the first sector to generate a second read signal; and
processing the second read signal to verify the defect in the first sector relative to the adjusted defect threshold.
14. The method as recited in claim 13 , wherein the first sector comprises a data sector.
15. The method as recited in claim 13 , wherein the first sector comprises a servo sector.
16. The method as recited in claim 14 , further comprising mapping out the data sector after the defect is detected relative to the adjusted defect threshold.
17. The method as recited in claim 13 , wherein adjusting the defect threshold comprises increasing the defect threshold.
18. The method as recited in claim 13 , wherein adjusting the defect threshold comprises decreasing the defect threshold.
19. The method as recited in claim 13 , wherein the defect threshold is adjusted to decrease the probability that the defect will be detected relative to the adjusted defect threshold.
20. The method as recited in claim 13 , wherein after adjusting the defect threshold further comprising:
rereading the first sector N number of times and track each time the defect is detected relative to the adjusted defect threshold; and
mapping out a data sector if the defect is detected more than once.
21. The method as recited in claim 20 , wherein the data sector is mapped out if the defect is detected at least M out of N times, where M is less than N.
22. The method as recited in claim 13 , wherein processing the first and second read signals to detect the defect comprises detecting an amplitude of the first and second read signals.
23. The method as recited in claim 13 , wherein processing the first and second read signals to detect the defect comprises detecting an estimated data sequence.
24. The method as recited in claim 13 , wherein processing the first and second read signals to detect the defect comprises demodulating embedded servo sectors written on the disk.
25. A disk drive comprising:
a disk comprising a plurality of sectors;
a head actuated radially over the disk; and
a means for initializing a defect threshold;
a means for reading a first sector to generate a first read signal;
a means for processing the first read signal to detect a defect in the first sector relative to the defect threshold;
after the defect is detected, a means for adjusting the defect threshold;
a means for rereading the first sector to generate a second read signal; and
a means for processing the second read signal to verify the defect in the first sector relative to the adjusted defect threshold.