SSD Garbage Collection Using VTC Velocity for Hot-Cold Data Separation
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Solution Overview
Problem
Traditional garbage collection (GC) strategies in solid state drives (SSDs) inefficiency in distinguishing between 'hot' and 'cold' data, leading to unnecessary data movement and increased write amplification (WA), particularly in workloads with limited logical block address (LBA) ranges, and existing complex solutions add overhead and complexity.
Innovation Solution
A memory controller that tracks valid translation unit count (VTC) velocity of memory device portions and selectively performs GC operations based on VTC velocities, transitioning to a greedy approach when necessary, to efficiently separate hot and cold data and reduce WA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional GC strategies are used, then GC operations can be performed, but write amplification increases and performance deteriorates due to inability to distinguish hot and cold data
Solution Approach 1:
The system pre-calculates and stores VTC (Valid Translation Unit Count) values for different data portions before GC operations are needed. This preliminary tracking of valid data units allows the GC algorithm to quickly identify cold data portions without performing complex analysis during the actual GC operation, thereby reducing write amplification and improving GC efficiency
Solution Approach 2:
The invention introduces VTC as a new parameter to characterize data portions, replacing traditional GC selection methods. By changing the selection criterion from simple LBA range or age-based metrics to VTC-based metrics, the system can effectively distinguish between hot and cold data, reducing unnecessary data movement and write amplification
2Productivity
If complex solutions are used to distinguish hot and cold data, then GC efficiency improves, but system complexity increases
Solution Approach 1:
The system segments the data storage space into multiple portions and calculates VTC values independently for each portion. This segmentation allows the complex GC decision-making process to be distributed across multiple simple VTC calculations rather than requiring one complex global analysis, reducing overall system complexity while maintaining GC efficiency
Solution Approach 2:
The VTC value serves as an intermediary parameter that simplifies the GC decision process. Instead of directly analyzing complex data access patterns to distinguish hot and cold data, the system uses VTC as an intermediate metric that captures the essential characteristics needed for GC selection, thereby reducing system complexity
Data Source
AI summary
This disclosure is directed to a memory device that performs garbage collection (GC) operations intelligently. The memory device generates a request to perform a GC operation on data stored on the memory device and, in response, accesses a valid translation unit count (VTC) velocity of each portion of a plurality of portions of the data stored on the memory device. The memory device selects an individual portion of the plurality of portions based on the VTC velocity of the individual portion and performs the GC operation on the selected individual portion.