Staggered Garbage Collection Unit Allocation for SSD I/O Consistency
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Solution Overview
Problem
In solid-state drives (SSDs) with non-volatile memory, concurrent access by multiple users can lead to significant variations in I/O transfer rates due to the relative arrangement of dies, channels, and garbage collection units (GCUs), resulting in inconsistent performance.
Innovation Solution
The SSDs are configured with staggered GCUs, where each GCU encompasses memory units from different combinations of dies, ensuring each die contributes to a consistent ratio of GCUs, and parity data sets are used for error protection, facilitating consistent transfer rate performance and better wear leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GCUs are arranged in traditional configurations, then the structure is simple to manage, but I/O transfer rate performance varies significantly among multiple users
Solution Approach 1:
The patent segments the storage device into multiple GCUs distributed across different dies, with each GCU assigned to specific users. This segmentation allows independent management of GCUs per user, ensuring consistent I/O performance by preventing interference between users' data access operations.
Solution Approach 2:
The patent applies local quality by assigning different GCU configurations to different users based on their specific performance requirements. Each user receives GCUs with optimized characteristics for their workload, allowing tailored performance optimization while maintaining overall system consistency.
2Productivity
If GCUs are allocated to accommodate all dies, then storage capacity is maximized, but wear distribution becomes uneven and performance becomes inconsistent
Solution Approach 1:
The patent implements dynamic GCU allocation where the controller can flexibly assign and reassign GCUs to different users based on real-time wear conditions and performance requirements. This dynamic approach ensures even wear distribution while maintaining optimal performance for each user.
Solution Approach 2:
The system incorporates feedback mechanisms where the controller monitors wear status and performance metrics of GCUs, then adjusts GCU assignments accordingly. This feedback loop enables the system to balance wear distribution and maintain consistent performance across all users.
3Productivity
If multiple users access data concurrently, then system productivity increases, but I/O transfer rate variations occur due to die arrangement
Solution Approach 1:
The patent segments the storage space into user-specific GCUs, allowing concurrent access by multiple users without interference. Each user's GCUs are isolated from others, ensuring that I/O operations for different users proceed independently with consistent performance characteristics.
Solution Approach 2:
The patent employs asymmetric GCU allocation strategies where different users may receive different numbers and configurations of GCUs based on their individual performance requirements and workload characteristics, enabling optimized concurrent access for each user.
Data Source
AI summary
Apparatus and method for managing a non-volatile memory (NVM) such as a flash memory in a solid-state drive (SSD). In some embodiments, the NVM is arranged as a plurality of semiconductor memory dies coupled to a controller circuit using a plurality of channels. The controller circuit divides the plurality of dies into a succession of garbage collection units (GCUs). Each GCU is independently erasable and allocatable for storage of user data. The GCUs are staggered so that each GCU is formed from a different subset of the dies in the NVM. In further embodiments, the dies are arranged into NVM sets in accordance with the NVMe (Non-Volatile Memory Express) specification with each NVM set addressable by a different user for storage of data in a separate set of staggered GCUs.