Storage device, continuous-vibration detecting method, and control apparatus
A falling-time measuring unit acquires information indicating whether a magnetic disk drive is falling, from a fall sensor at a predetermined sampling cycle, and measures a falling time based on the acquired information. A threshold changing unit counts number of times the measured falling time exceeds a predetermined fall-determination threshold within a predetermined time, and extends the fall-determination threshold when the counted number of times exceeds a predetermined maximum number of times. A head retracting unit retracts the head to the retraction position when the measured falling time exceeds the extended fall-determination threshold.
1. A storage device that retracts a head on a storage medium to a predetermined retraction position upon detecting a fall, the storage device comprising:
a falling-time measuring unit that acquires information indicating whether the magnetic disk drive is falling, from a fall sensor at a predetermined sampling cycle, and measures a falling time based on the acquired information;
a threshold changing unit that counts number of times the measured falling time exceeds a predetermined fall-determination threshold within a predetermined time, and extends the fall-determination threshold when the counted number of times exceeds a predetermined maximum number of times; and
a head retracting unit that retracts the head to the retraction position when the measured falling time exceeds the extended fall-determination threshold.
2. The storage device according to claim 1 , wherein
when the counted number of times is below the maximum number of times, the threshold changing unit reduces the fall-determination threshold.
3. The storage device according to claim 1 , further comprising:
a sampling-cycle changing unit that changes the sampling cycle based on the measured falling time.
4. The storage device according to claim 3 , wherein
when the measured falling time exceeds a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit reduces the sampling cycle.
5. The storage device according to claim 4 , wherein
when the measured falling time is below a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit extends the sampling cycle.
6. The storage device according to claim 3 , wherein
when the measured falling time exceeds a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit advances the sampling cycle or delays the sampling cycle.
7. The storage device according to claim 3 , wherein
the sampling-cycle changing unit sets a plurality of sampling-cycle changing thresholds with different lengths in a stepwise manner, and sets a predetermined sampling cycle determined for each of sampling-cycle changing thresholds.
8. A continuous-vibration detecting method for a storage device that retracts a head on a storage medium to a predetermined retraction position upon detecting a fall, the continuous-vibration detecting method comprising:
falling-time measuring including
acquiring information indicating whether the magnetic disk drive is falling, from a fall sensor at a predetermined sampling cycle; and
measuring a falling time based on the acquired information;
threshold changing including
counting number of times the measured falling time exceeds a predetermined fall-determination threshold within a predetermined time; and
extending the fall-determination threshold when the counted number of times exceeds a predetermined maximum number of times; and
retracting the head to the retraction position when the measured falling time exceeds the extended fall-determination threshold.
9. The continuous-vibration detecting method according to claim 8 , wherein
when the counted number of times is below the maximum number of times, the threshold changing includes reducing the fall-determination threshold.
10. The continuous-vibration detecting method according to claim 8 , further comprising:
changing the sampling cycle based on the measured falling time.
11. The continuous-vibration detecting method according to claim 10 , wherein
when the measured falling time exceeds a predetermined sampling-cycle changing threshold, the changing includes reducing the sampling cycle.
12. The continuous-vibration detecting method according to claim 11 , wherein
when the measured falling time is below a predetermined sampling-cycle changing threshold, the changing includes extending the sampling cycle.
13. A computer program product comprising a computer usable medium having computer readable program codes embodied in the medium that when executed causes a computer to execute:
falling-time measuring including
acquiring information indicating whether the magnetic disk drive is falling, from a fall sensor at a predetermined sampling cycle; and
measuring a falling time based on the acquired information;
threshold changing including
counting number of times the measured falling time exceeds a predetermined fall-determination threshold within a predetermined time; and
extending the fall-determination threshold when the counted number of times exceeds a predetermined maximum number of times; and
retracting the head to the retraction position when the measured falling time exceeds the extended fall-determination threshold.
14. A control apparatus that controls a storage device that retracts a head on a storage medium to a predetermined retraction position upon detecting a fall, the control apparatus comprising:
a falling-time measuring unit that acquires information indicating whether the magnetic disk drive is falling, from a fall sensor at a predetermined sampling cycle, and measures a falling time based on the acquired information;
a threshold changing unit that counts number of times the measured falling time exceeds a predetermined fall-determination threshold within a predetermined time, and extends the fall-determination threshold when the counted number of times exceeds a predetermined maximum number of times; and
a head retracting unit that retracts the head to the retraction position when the measured falling time exceeds the extended fall-determination threshold.
15. The control apparatus according to claim 14 , wherein
when the counted number of times is below the maximum number of times, the threshold changing unit reduces the fall-determination threshold.
16. The control apparatus according to claim 14 , further comprising:
a sampling-cycle changing unit that changes the sampling cycle based on the measured falling time.
17. The control apparatus according to claim 16 , wherein
when the measured falling time exceeds a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit reduces the sampling cycle.
18. The control apparatus according to claim 17 , wherein
when the measured falling time is below a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit extends the sampling cycle.
19. The control apparatus according to claim 16 , wherein
when the measured falling time exceeds a predetermined sampling-cycle changing threshold, the sampling-cycle changing unit advances the sampling cycle or delays the sampling cycle.
20. The control apparatus according to claim 16 , wherein
the sampling-cycle changing unit sets a plurality of sampling-cycle changing thresholds with different lengths in a stepwise manner, and sets a predetermined sampling cycle determined for each of sampling-cycle changing thresholds.