Multi-Actuator Disk Scheduling to Mitigate Track-Following Disturbances
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Solution Overview
Problem
In multi-actuator data storage devices, the mechanical disturbances caused by one actuator's seek operations can interfere with the track-following operations of other actuators, leading to degraded performance and potential data corruption during write operations.
Innovation Solution
The scheduling of actuators is optimized by determining time periods when one actuator's seek operations will not impact the track-following of another, by adjusting the start time or seek profile of low-priority disk access operations, such as slowing acceleration and deceleration, to minimize cross-actuator disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If seek operations are performed at high priority to improve response time, then productivity is improved, but track-following stability of other actuators deteriorates due to mechanical disturbances
Solution Approach 1:
The system performs preliminary assessment of the disk medium state (read-only vs. read-write regions) before executing seek operations. Based on this preliminary information, the scheduler decides whether to allow seek operations during track-following periods or to reschedule them, preventing mechanical disturbances that would corrupt data in read-write regions while maintaining efficient seek performance in read-only regions.
Solution Approach 2:
The system dynamically adjusts seek operation scheduling based on real-time conditions of the disk medium and actuator states. The scheduler modifies seek timing and prioritization depending on whether the current track is read-only or read-write, and whether other actuators are performing track-following operations, creating a flexible adaptive scheduling strategy rather than fixed priority rules.
2Productivity
If parallel seek operations are performed by multiple actuators to increase throughput, then productivity is improved, but mechanical disturbances increase causing servo control degradation
Solution Approach 1:
The system applies different quality control rules to different regions of the disk medium. Read-only regions allow aggressive parallel seek operations with minimal restrictions, while read-write regions impose strict constraints on parallel seeks to prevent mechanical disturbances that could corrupt data. This localized quality approach enables high throughput in safe regions while protecting critical data regions.
Solution Approach 2:
The system uses feedback from the disk medium state (identifying read-only vs. read-write regions) to dynamically control parallel seek operations. The scheduler continuously monitors which actuators are performing track-following operations and adjusts the scheduling of parallel seeks accordingly, allowing parallel operations when safe and preventing them when they would cause harmful disturbances.
3Reliability
If seek operations are delayed to avoid mechanical disturbances, then track-following stability is improved, but seek response time increases
Solution Approach 1:
The system changes the operational parameters of seek operations based on the disk medium state. In read-only regions, seeks can proceed at normal speed and priority without delay. In read-write regions during track-following operations, the system changes parameters by delaying seeks or reducing their priority, balancing the need for stability with acceptable response time based on the criticality of the region.
Data Source
AI summary
A first time period is determined during which a first head driven by a first actuator will be performing a track-following operation. A second time period is also determined during which a second head driven by a second actuator will be performing a low-priority disk access operation that includes a seek. 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 seek of the second head will impact servo control of the track-following operation of the first head, a start time of the seek of the second head is changed to correspond to a time that mitigates impacts to the track-following operation of the first head.