Disk drive modifying an update function for a refresh monitor in response to a measured duration

1. A disk drive comprising:

a disk;

a head actuated over the disk; and

control circuitry operable to:

maintain a refresh monitor for data stored on the disk, wherein the refresh monitor comprises an update function responsive to an operating parameter of the disk drive;

maintain a duration monitor;

modify the update function of the refresh monitor in response to the duration monitor; and

refresh the data stored on the disk in response to the refresh monitor.

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

the disk comprises a plurality of refresh zones; and

the refresh monitor comprises a plurality of refresh monitors each corresponding to a respective refresh zone.

3. The disk drive as recited in claim 1 , wherein the duration monitor tracks a data-lifetime duration after writing data to the disk.

4. The disk drive as recited in claim 1 , wherein the duration monitor tracks a drive-lifetime duration after manufacturing the disk drive.

5. The disk drive as recited in claim 1 , wherein the operating parameter comprises an ambient temperature.

6. The disk drive as recited in claim 1 , wherein the operating parameter comprises a fly-height heater parameter.

7. The disk drive as recited in claim 1 , wherein the operating parameter comprises a data density of data recorded on the disk.

8. The disk drive as recited in claim 1 , wherein the operating parameter comprises at least one of an ambient temperature, altitude, a fly-height heater parameter, a write current amplitude, a write current overshoot, a skew angle of the head, a width of the head, a data density of data recorded on the disk, and a servo parameter.

9. The disk drive as recited in claim 1 , wherein the update function comprises at least one coefficient, and the update function is modified by modifying the coefficient.

10. A method of operating a disk drive, the disk drive comprising a disk, and a head actuated over the disk, the method comprising:

maintaining a refresh monitor for data stored on the disk, wherein the refresh monitor comprises an update function responsive to an operating parameter of the disk drive;

maintaining a duration monitor;

modifying the update function of the refresh monitor in response to the duration monitor; and

refreshing the data stored on the disk in response to the refresh monitor.

11. The method as recited in claim 10 , wherein:

the disk comprises a plurality of refresh zones; and

the refresh monitor comprises a plurality of refresh monitors each corresponding to a respective refresh zone.

12. The method as recited in claim 10 , wherein the duration monitor tracks a data-lifetime duration after writing data to the disk.

13. The method as recited in claim 10 , wherein the duration monitor tracks a drive-lifetime duration after manufacturing the disk drive.

14. The method as recited in claim 10 , wherein the operating parameter comprises an ambient temperature.

15. The method as recited in claim 10 , wherein the operating parameter comprises a fly-height heater parameter.

16. The method as recited in claim 10 , wherein the operating parameter comprises a data density of data recorded on the disk.

17. The method as recited in claim 10 , wherein the operating parameter comprises at least one of an ambient temperature, altitude, a fly-height heater parameter, a write current amplitude, a write current overshoot, a skew angle of the head, a width of the head, a data density of data recorded on the disk, and a repeatable runout parameter.

18. The method as recited in claim 10 , wherein the update function comprises at least one coefficient, and the update function is modified by modifying the coefficient.

19. A disk drive comprising:

a disk;

a head actuated over the disk; and

control circuitry operable to:

maintain a refresh monitor for data stored on the disk;

maintain a duration monitor operable to track a drive-lifetime of the disk drive;

modify the refresh monitor in response to the duration monitor; and

refresh the data stored on the disk in response to the refresh monitor.

20. The disk drive as recited in claim 19 , wherein:

the refresh monitor comprises an update function responsive to an operating parameter of the disk drive; and

the control circuitry is further operable to modify the update function of the refresh monitor in response to the duration monitor.

21. A disk drive comprising:

a disk;

a head actuated over the disk;

a means for maintaining a refresh monitor for data stored on the disk, wherein the refresh monitor comprises a first update function responsive to an operating parameter of the disk drive;

a means for maintaining a duration monitor;

a means for modifying the first update function of the refresh monitor in response to the duration monitor; and

a means for refreshing the data stored on the disk in response to the refresh monitor.

22. The disk drive as recited in claim 21 , wherein:

the duration monitor comprises a means for tracking a data-lifetime duration of the data stored on the disk and a drive-lifetime duration of the disk drive; and

the first update function is modified in response to the data-lifetime duration and the drive-lifetime duration.

23. The disk drive as recited in claim 21 , wherein:

the duration monitor comprises a means for tracking a data-lifetime duration of the data stored on the disk and a drive-lifetime duration;

the first update function is modified in response to the data-lifetime duration;

the refresh monitor comprises a second update function operable to track a refresh interval; and

further comprising a means for modifying the second update function in response to the drive-lifetime duration.