Granted Patent B1

US 9,117,481 · App. 12/471,265 · Granted Aug 25, 2015

Abstract

Claims (42)

1. A disk drive comprising:

a disk;

a head;

a ramp located near an outer periphery of the disk; and

control circuitry operable to:

load the head off the ramp over the disk;

receive a first unload command to perform an unload operation;

evaluate a number of unloads relative to an unload limit that varies over time; and

when the number of unloads exceeds the unload limit, delay the unload operation.

2. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:

increment a delay counter when delaying the first unload operation;

receive an access command when delaying the first unload operation;

execute the access command without resetting the delay counter, and receive a second unload command after executing the access command; and

when the delay counter exceeds a threshold, unload the head onto the ramp.

3. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to delay the unload operation for a predetermined interval.

4. The disk drive as recited in claim 3 , wherein the control circuitry is further operable to vary the predetermined interval.

5. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to delay the unload when the number of unloads exceeds the unload limit by a delay threshold.

6. The disk drive as recited in claim 5 , wherein the control circuitry is further operable to delay the unloads until the number of unloads falls below the unload limit.

7. The disk drive as recited in claim 5 , wherein the control circuitry is further operable to adjust the delay threshold over a life of the disk drive.

8. The disk drive as recited in claim 5 , wherein the control circuitry is further operable to delay the unload operation over a varying interval relative to the adjusted delay threshold.

9. The disk drive as recited in claim 1 , wherein the control circuitry is further operable to:

measure an ambient temperature of the disk drive; and

adjust the unload limit in response to the ambient temperature.

10. A method of operating a disk drive, the disk drive comprising a disk, a head, and a ramp located near an outer periphery of the disk, the method comprising:

loading the head off the ramp over the disk;

receiving a first unload command to perform an unload operation;

evaluating a number of unloads relative to an unload limit that varies over time; and

when the number of unloads exceeds the unload limit, delaying the unload operation.

11. The method as recited in claim 10 , further comprising:

incrementing a delay counter when delaying the first unload operation;

receiving an access command when delaying the first unload operation;

executing the access command without resetting the delay counter, and receiving a second unload command after executing the access command; and

when the delay counter exceeds a threshold, unloading the head onto the ramp.

12. The method as recited in claim 10 , further comprising delaying the unload operation for a predetermined interval.

13. The method as recited in claim 12 , further comprising varying the predetermined interval.

14. The method as recited in claim 10 , further comprising delaying the unload when the number of unloads exceeds the unload limit by a delay threshold.

15. The method as recited in claim 14 , further comprising delaying the unloads until the number of unloads falls below the unload limit.

16. The method as recited in claim 14 , further comprising adjusting the delay threshold over a life of the disk drive.

17. The method as recited in claim 14 , further comprising delaying the unload operation over a varying interval relative to the adjusted delay threshold.

18. The method as recited in claim 10 , further comprising:

measuring an ambient temperature of the disk drive; and

adjusting the unload limit in response to the ambient temperature.

Assignments (8)