Disk Drive Shutdown via Back-EMF Power and Segmented Actuator Control
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Solution Overview
Problem
Current hard disk drives (HDDs) face challenges in managing unexpected shutdowns, particularly in systems with multiple actuators and controllers, where the kinetic energy from spinning disks may be insufficient to perform all necessary safeguarding operations, leading to potential data loss and physical damage.
Innovation Solution
A method and apparatus that utilize the back-electromotive force (BEMF) of a motor driven by spinning disks to power a shutdown procedure, where both controllers independently move their respective actuators to safe positions and write cache data to non-volatile memory, coordinating the actions to prevent power spikes and ensure data preservation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators and controllers are used to increase productivity, then the rate of input/output operations is improved, but the kinetic energy available during unexpected shutdown becomes insufficient to perform all necessary safeguarding operations
Solution Approach 1:
The system divides the safeguarding operations into separate independent tasks for each controller-actuator pair. Each controller independently manages its own actuator's positioning and cache data writing, rather than requiring centralized coordination that would consume additional energy. This segmentation allows parallel execution of safeguarding operations across multiple controller-actuator pairs.
Solution Approach 2:
The system performs actuator positioning to safe positions before writing cache data to non-volatile memory. By completing the mechanical positioning operations first while kinetic energy is still available, the system prepares the system state in advance so that subsequent data writing can proceed with reduced power requirements.
2Reliability
If all actuators are moved to safe positions and cache data is written during unexpected shutdown, then data loss and physical damage are prevented, but the power requirements exceed the available kinetic energy from spinning disks
Solution Approach 1:
The shutdown procedure is segmented into independent parallel operations where each controller-actuator pair operates autonomously. This eliminates the need for sequential execution that would accumulate total power requirements, and instead allows simultaneous execution where each pair draws power independently from the available kinetic energy pool.
Solution Approach 2:
Each controller independently manages its own actuator positioning and cache data writing without requiring coordination or additional power management from a central controller. The controllers autonomously determine when their respective actuators reach safe positions and when to initiate cache writing, reducing overall system power requirements.
3Reliability
If controllers coordinate their actions to prevent power spikes, then reliable shutdown is achieved, but system complexity increases
Solution Approach 1:
The system eliminates the need for complex inter-controller coordination by segmenting the shutdown function into independent controller-actuator pairs. Each controller operates autonomously based on local feedback from its own actuator position sensors and cache write status, avoiding the need for complex communication and coordination protocols between multiple controllers.
Solution Approach 2:
Each controller continuously monitors its own actuator position and cache write status, using this feedback to determine when to initiate and complete safeguarding operations. This local feedback mechanism replaces complex centralized coordination while ensuring reliable shutdown execution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively manages unexpected shutdowns by ensuring safe positioning of actuators and data backup, even when kinetic energy is limited, thereby preventing data loss and physical damage, and optimizing power usage during shutdowns in HDDs with parallelism architectures.
Implementation Method 1
receiving power for the hard disk drive via back-electromotive force of a motor driven by the one or more spinning disks
Data Source
AI summary
An event that indicates unexpected shutdown of a hard disk drive is determined. The hard disk includes first and second controllers that control respective first and second independently-operable actuators. Each of the actuators has one or more heads that access one or more spinning disks of the hard disk drive. While receiving power for the hard disk drive via back-electromotive force of a motor driven by the one or more spinning disks in response to the event, the first and second controllers independently move the respective first and second actuators to safe positions. In response to determining the first and second actuators are in safe positions, write cache data associated with the first and second controllers is written to a non-volatile memory.