Multi-Actuator HDD Servo Control Scheduling
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Solution Overview
Problem
In hard disk drives with multiple actuators, the mechanical disturbances caused by one actuator's movement can interfere with the operations of other actuators, leading to degraded performance, particularly during seek acceleration and deceleration, which can result in mistracking and delayed or suspended write operations.
Innovation Solution
The scheduling of actuator operations is optimized by translating potential disturbance and susceptibility data into time regions, allowing for the minimization of cross-actuator interference by adjusting the timing of operations, such as delaying or modifying seek states, to reduce the impact on servo control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators perform disk access operations in parallel to increase productivity, then the throughput and IOPS improve, but mechanical disturbances from one actuator interfere with other actuators, degrading servo control and causing mistracking
Solution Approach 1:
The system performs preliminary scheduling of actuator operations by translating disturbance and susceptibility data into time regions. This allows the controller to pre-determine optimal timing for each actuator's seek, track, and write operations, ensuring that high-impact operations are scheduled when mechanical disturbances are minimal, thereby preventing mistracking before it occurs
Solution Approach 2:
The system dynamically adjusts actuator operation timing based on real-time disturbance and susceptibility profiles. By making the scheduling flexible and adaptive rather than fixed, the system can optimize the timing of each actuator's movements to minimize mechanical interference with other actuators while maintaining high throughput
2Speed
If seek acceleration and deceleration are performed at high rates to improve access speed, then productivity increases, but mechanical disturbances increase causing mistracking and degraded servo control
Solution Approach 1:
The system pre-calculates optimal seek trajectories and timing by translating disturbance data into time regions before operations execute. This allows high-speed seeks to be scheduled at times when mechanical disturbances will not affect tracking precision, maintaining both speed and accuracy
Solution Approach 2:
The system uses disturbance and susceptibility data as feedback to adjust scheduling decisions. By continuously monitoring and using this feedback to optimize timing, the system maintains tracking precision even during high-speed operations
3Productivity
If write operations are scheduled to maximize throughput, then productivity improves, but mechanical disturbances from concurrent operations cause delayed or suspended write operations
Solution Approach 1:
The system performs preliminary scheduling of write operations by translating susceptibility data into time regions. This allows the controller to identify optimal time windows for writing data, scheduling them when mechanical disturbances are minimal, thereby preventing delays and suspensions while maintaining high throughput
Data Source
AI summary
In a disk drive apparatus, a first time period is determined, during which a first head driven by a first actuator will be performing a first disk access operation. A second time period is determined, during which a second head driven by a second actuator will be performing a second disk access operation. The first and second actuators are independently movable such that the first and second disk access operations are capable of being performed in parallel. If it is determined that the second disk access operation will impact servo control of the first disk access operation, at least one of the first and second disk access operations is changed to reduce the impact to the servo control of the first disk access operation.