Split Actuator HDD Scheduling for Positioning Accuracy
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Solution Overview
Problem
Magnetic hard disk drives (HDDs) with multiple rotary actuators face challenges in maintaining positioning accuracy due to mechanical interactions between actuators, where high accelerations and changes in acceleration from one actuator can significantly affect the positioning of another actuator, leading to reduced accuracy during data access operations.
Innovation Solution
The implementation of a method to schedule disk access commands in a split-actuator HDD, where the execution of commands is coordinated to minimize disturbances between actuators, including selecting and modifying disk access operations to avoid coincidence with critical times of other actuators' operations, and synchronizing seek operations to ensure simultaneous seeking by both actuators, thereby reducing acceleration-related disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators operate simultaneously to increase throughput, then data access performance is improved, but positioning accuracy deteriorates due to mechanical interactions and vibrations between actuators
Solution Approach 1:
The system performs preliminary scheduling of disk access commands to determine optimal execution timing. By calculating disturbance time intervals for each actuator based on their current and historical operations, the system proactively identifies when high-acceleration seek operations will occur and uses this information to coordinate actuator operations, preventing vibrations from affecting other actuators during critical moments.
Solution Approach 2:
The system dynamically adjusts actuator operation timing based on real-time conditions. The controller continuously monitors and updates disturbance time intervals as actuators perform operations, modifying the scheduling decisions adaptively. This dynamic coordination allows the system to maintain high throughput while preventing mechanical interference between actuators during seek operations.
2Productivity
If high acceleration seek operations are performed to reduce access time, then productivity is improved, but mechanical disturbances increase that affect other actuators
Solution Approach 1:
The system calculates disturbance time intervals in advance by analyzing the acceleration profiles of upcoming seek operations. By determining when high-acceleration phases will occur, the controller can proactively schedule other actuator operations to avoid these disturbance periods, thereby maintaining fast seek operations while minimizing their harmful mechanical effects on other actuators.
Solution Approach 2:
The system converts the harmful disturbance time information into a beneficial scheduling parameter. By identifying when vibrations and mechanical disturbances will occur during seek operations, the controller uses this knowledge to coordinate other actuator operations to avoid these periods, effectively turning the potentially harmful high-acceleration phases into scheduled events that can be workarounded by other actuators.
Data Source
AI summary
Systems and methods for scheduling the execution of disk access commands in a split-actuator hard disk drive are provided. In some embodiments, while a first actuator of the split actuator is in the process of performing a first disk access command (a victim operation), a second disk access command (an aggressor operation) is selected for and executed by a second actuator of the split actuator. The aggressor operation is selected from a queue of disk access commands for the second actuator, and is selected based on being the disk access command in the queue that can be initiated sooner than any other disk access command in the queue without disturbing the victim operation.