SSD Read Hotness Detection with Global and Local Counters
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Solution Overview
Problem
Existing methodologies for detecting read disturb in SSDs are inadequate for emerging SSD designs, leading to excessive memory usage and unnecessary data relocations due to the inability to accurately track read hotness and randomness, which traditional block-based strategies cannot address.
Innovation Solution
Implementing a read hotness and degree of randomness detector that utilizes global and local read counters, read hotness bit arrays, collision counters, and hot read zone counters to efficiently track and mitigate read disturbances, reducing memory requirements from GBs to MBs and minimizing data relocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional block-based read disturb detection is used, then the method is simple to implement, but it cannot accurately track read hotness and randomness leading to excessive memory usage and unnecessary data relocations
Solution Approach 1:
The patent segments the detection mechanism into multiple components: global read counters for overall read volume, local read counters for zone-specific reads, read hotness bit arrays for tracking accessed blocks, collision counters for detecting read patterns, and hot read zone counters for identifying high-activity zones. This segmentation enables precise tracking of read hotness and randomness at different granularities, resolving the contradiction between detection accuracy and implementation complexity.
2Reliability
If traditional block-based detection is used, then the implementation is straightforward, but memory usage becomes excessive and data relocations increase unnecessarily
Solution Approach 1:
The patent implements dynamic detection thresholds and adaptive data relocation strategies based on real-time read hotness and randomness metrics. The system dynamically adjusts relocation decisions based on collision counter values and hot read zone identification, ensuring data reliability is maintained while minimizing unnecessary relocations and memory usage compared to static traditional approaches.
3Productivity
If read hotness and randomness are accurately tracked, then data relocation decisions improve, but the detection mechanism becomes more complex
Solution Approach 1:
The patent merges multiple detection functions into a unified detector structure that simultaneously tracks global read volume, local zone reads, block-level hotness, and zone-level randomness. This consolidation enables efficient data relocation decisions through integrated metrics while avoiding the overhead of separate independent detection systems, resolving the contradiction between relocation efficiency and detector complexity.
Data Source
AI summary
A request to read data stored in a non-volatile memory (NVM) is processed by incrementing a global read counter for the NVM, incrementing a local read counter for a zone of the NVM being accessed by processing of the read request, computing a degree of read hotness for the zone, computing a read concentration of the zone based at least in part on the degree of read hotness of the zone, the global read counter, and the local read counter, and relocating the data in the NVM when the read concentration of the zone meets or exceeds a threshold.