Shared Disk Configuration in Multiple Actuator Hard Disk Drives
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Solution Overview
Problem
High-capacity hard disk drives face challenges in scaling performance with increasing storage capacity, particularly in reducing latency and optimizing actuator systems for efficient data access in multi-actuator configurations, where mechanical constraints and space utilization hinder efficient disk spacing and actuator arm arrangements.
Innovation Solution
Implementing a dual-actuator shared disk system with optimized disk spacing, arm tip thickness, and suspension tail biasing to enhance z-height utilization, allowing for better electrical trace routing and maintaining consistent head-gimbal assembly/suspension z-heights across all arms, thereby improving actuator performance and reducing track mis-registration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple actuators are implemented to increase IOPs density, then data access performance is improved, but mechanical constraints and space utilization worsen, hindering efficient disk spacing and actuator arm arrangements
Solution Approach 1:
The patent implements a shared-disk configuration where a single physical disk is accessed by multiple actuators through different surfaces (top and bottom). This merging of disk resources allows multiple actuators to operate on the same disk medium, increasing IOPs density without proportionally increasing the number of physical disks, thereby managing mechanical space constraints more effectively.
Solution Approach 2:
The patent utilizes the z-dimension (vertical spacing) by implementing asymmetric disk spacing where the shared disk is positioned at a different z-height from adjacent disks. This dimensional approach allows actuators to access the shared disk from opposite sides without mechanical interference, resolving the conflict between multiple actuators and mechanical constraints.
2Volume of moving object
If disk spacing is optimized for multi-actuator configuration, then z-height utilization is improved, but electrical trace routing becomes more challenging
Solution Approach 1:
The patent implements asymmetric disk spacing where the shared disk has different spacing from adjacent disks, creating localized variations in z-height. This local quality approach optimizes the z-space utilization for the shared disk while maintaining standard spacing for other disks, allowing electrical trace routing to be managed in standardized regions while achieving optimized vertical space utilization in the shared disk region.
3Quantity of substance
If actuator arm configurations are optimized for shared disk access, then capacity utilization is improved, but track mis-registration increases
Solution Approach 1:
The patent implements asymmetric actuator arm configurations where arms serving the shared disk have different characteristics (such as arm tip thickness) compared to arms serving non-shared disks. This asymmetry allows optimization of the moment of inertia for shared disk access while maintaining precise track following, thereby improving capacity utilization without significantly increasing track mis-registration.
Data Source
AI summary
A multiple-actuator hard disk drive includes multiple head-stack assemblies (HSA) and a disk stack including a shared disk operated upon by both of the HSAs. Generally to provide more space between the HSAs such as for routing electrical traces, the distance between the shared disk and each of the upper and lower adjacent disks is greater than the distance between each of the upper and lower adjacent disks and the next adjacent disk. Each arm tip of the arms operating upon the shared disk may be thicker than other arm(s) operating upon other disks in the stack, so that the z-height between each head slider and corresponding disk surface is maintained in view of the differing disk spacing. Suspension tails for the arms that operate on the shared disk may be biased to offset away from the shared disk to provide for more clearance between the HSAs.