The most commonly used data storage means for computers are hard-disk drives (HDDs) having structures in which one or more magnetic disks are disposed coaxially and driven by a spindle motor. Data reading and writing are done by magnetic heads provided in opposition to the magnetic disks. The magnetic heads are driven by an actuator, generally a voice coil motor (“VCM”). The magnetic disks, the magnetic heads, and the actuator are stored in a housing called an enclosure case.
Typically, computer systems, including desktop and portable computers, may operate in a power saving mode of operation in order to reduce power consumption. One such power saving mode of operation may be referred to as a “standby mode.” In the standby mode of operation, the display may be deactivated or turned down, the central processing unit may be operating in a lower-power mode of operation and the hard disk drive may be deactivated. A computer system may be invoked to enter a standby mode of operation after a period of inactivity, e.g., five minutes, or upon a user invoking the computer system to enter the standby mode of operation. The “sleeping” computer system may be “awakened” or resumed upon an event such as a user's keystroke, pressing the power button, receipt of electronic mail, a fax, etc. That is, upon an awakening event, the computer system exits out of the standby mode of operation and resumes a normal mode of operation.
As stated above, when the computer system enters a standby mode of operation, the hard disk drive becomes deactivated. When that occurs, the spindle motor is deactivated and the magnetic heads are lifted by the actuator to be “parked” outside of the stack of one or more magnetic disks onto a “ramp”. This may be referred to herein as a “spin-down” cycle. When the computer system resumes the normal mode of operation, the spindle motor is activated and the magnetic heads are lifted by the actuator to be moved from the ramp to the stack of one or more magnetic disks. This may be referred to herein as a “spin-up” cycle.
The spindle motor may be designed to handle a certain number of spin-up/spin-down cycles over the lifetime of the spindle motor. If a computer system is repeatedly entering and exiting to and from the standby mode of operation, it may be possible that the number of spin-up/spin-down cycles may exceed the number of spin-up/spin-down cycles the spindle motor is designed to handle over its lifetime.
Therefore, there is a need in the art to ensure that the number of spin-up/spin-down cycles for a spindle motor in a hard disk drive does not exceed the rate the spindle motor is designed to handle.
Furthermore, the computer system may enter and exit the standby mode of operation in a rather short period of time. Applications that have low, but very repetitive access patterns, may invoke the computer system to reenter the normal mode of operation just after entering the standby mode of operation. For example, an anti-virus application operating on the computer system may issue a command just after the computer system enters the standby mode of operation. This command will then awaken the computer system to enter the normal mode of operation. Quickly exiting the standby mode of operation to resume a normal mode of operation may produce a lot of stress on the spindle motor. Spindle motors may be fluid dynamic bearing motors which utilize a viscous oil rather than metal ball bearings. By quickly exiting the standby mode of operation to resume the normal mode of operation, a “cavitation” may form in the viscous oil thereby causing the oil to not be smoothly uniform which may lead to mechanical friction which increases wear on the spindle motor. Hence, by having many short spin-up/spin-down cycles, the spindle motor may wear out faster than designed due to the cavitations formed in the viscous oil.
Therefore, there is a need in the art to ensure that the duration of the spin-down cycle is not too short thereby reducing, at least in part, excessive wear on the spindle motor.
Furthermore, computer systems may enter another power saving mode of operation commonly referred to as “low power idle” state. In the “low power idle” state of operation, the processor operates in a lower-power mode of operation. Furthermore, during the low power idle state of operation, the magnetic heads are parked onto a ramp as in the standby mode of operation. However, during the low power idle state of operation, the spindle motor continues to spin. As stated above, the spindle motor becomes deactivated, i.e., stops spinning, during the standby mode of operation.
A computer system may enter the low power idle state after a shorter period of inactivity than required for the computer system to enter the standby mode of operation as described above. For example, if the computer system is idle for 30 seconds, then the computer system may enter the low power idle state of operation. If the computer system continues to be idle for five minutes, then the computer system enters the standby mode of operation.
As stated above, during the lower power idle state of operation, the magnetic heads are parked onto the ramp. This may be referred to herein as a “unload” cycle. When the computer system resumes the normal mode of operation, the magnetic heads are lifted by the actuator to be moved from the ramp to the stack of one or more magnetic disks. This may be referred to herein as a “load” cycle.
The actuator may be designed to handle a certain number of load/unload cycles, e.g., 300,000 load/unload cycles, over the lifetime of the actuator. If a computer system is repeatedly entering and exiting to and from the low power idle state of operation, it may be possible that the number of load/unload cycles exceeds the number of load/unload cycles the actuator is designed to handle over its lifetime.
Therefore, there is a need in the art to ensure that the number of load/unload cycles for an actuator in a hard disk drive does not exceed the rate the actuator is designed to handle.