Shared Read Channel Scheduling in Multi-Actuator HDDs
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Solution Overview
Problem
The high manufacturing costs associated with multi-actuator hard disk drives (HDDs) due to the duplication of read and write channels hinder their widespread adoption, despite their potential for improved read and write throughput.
Innovation Solution
A multi-actuator HDD design with a shared read channel and a job scheduler that employs a lowest-access-time selection methodology to schedule concurrent operations, allowing one actuator to read while the other seeks or writes, thereby optimizing read throughput and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple read channels are duplicated to enable simultaneous reads from multiple actuators, then read throughput is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple read channels into a single shared read channel that is time-multiplexed across multiple actuators. Instead of providing dedicated read channels for each actuator, the system combines the read channel resources and allocates them to different actuators at different time slots, thereby reducing manufacturing cost while maintaining the capability to service multiple actuators.
Solution Approach 2:
The patent implements dynamic scheduling of the shared read channel across multiple actuators based on real-time需求的. The read channel is dynamically assigned to different actuators depending on which actuator has data ready to be read, allowing the system to adapt to varying workload conditions and maximize throughput without requiring static dedicated channels for each actuator.
2Ease of manufacture
If a shared read channel is used to reduce manufacturing cost, then production cost decreases, but read throughput may be degraded due to channel contention
Solution Approach 1:
The patent employs preliminary action by implementing a scheduler that proactively manages read channel allocation before conflicts occur. The scheduler monitors the state of multiple actuators and preemptively assigns the shared read channel to actuators that are ready to read, preventing channel contention and idle time. This advance planning ensures that the shared channel is always productively utilized without degradation in throughput.
Solution Approach 2:
The patent implements periodic action through time-multiplexed allocation of the shared read channel to different actuators in periodic time slots. The channel is systematically assigned to Actuator 1, then Actuator 2, then Actuator 3, and so on, creating a periodic schedule that ensures each actuator receives fair access to the read channel while maintaining high overall throughput.
3Productivity
If concurrent operations are scheduled without intelligent scheduling, then device utilization improves, but access time increases due to channel conflicts
Solution Approach 1:
The patent implements feedback mechanisms where the scheduler continuously monitors the status of multiple actuators, including which actuators have data ready in their buffers, current read/write operations in progress, and channel availability. This feedback information is used to dynamically adjust the scheduling decisions, assigning the shared read channel to the actuator that is ready and will minimize access time, thereby reducing channel conflicts and overall access time while maintaining high device utilization.
Data Source
AI summary
A multi-actuator storage device includes a first actuator supporting a first read element coupled to a shared read channel, a second actuator supporting a second read element coupled to the shared read channel, and a job scheduler that employs a lowest-access time selection methodology when selecting each next job to schedule on the first actuator. When the lowest-access-time methodology results in the selection of a read job for execution by the first actuator, the job scheduler identifies a pending job for execution by the second actuator that can be executed concurrent to the first read job without concurrently accessing the read channel and schedules the pending job on the second actuator concurrent to the first read job.