Nonvolatile Memory Wear-Leveling Copy Modes for Erase Balance
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Solution Overview
Problem
Existing nonvolatile memory systems face challenges in dynamically controlling the number of erase operations across blocks to prevent excessive wear and extend the lifespan of the memory system.
Innovation Solution
A memory system with a controller that executes a wear-leveling copy operation, copying valid data from blocks with fewer erase cycles to those with more cycles, using different modes (normal and acceleration) based on threshold differences and cumulative data write amounts to balance erase cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If wear-leveling copy operation is executed frequently to balance erase cycles, then lifespan of memory system is extended, but processing time and system performance are reduced
Solution Approach 1:
The patent dynamically changes the parameter of copy amount in wear-leveling operations based on the difference in erase cycle counts between blocks. When the difference exceeds a threshold, larger copy amounts are used to accelerate wear-leveling; when the difference is small, smaller copy amounts are used to minimize performance impact. This adaptive parameter adjustment resolves the contradiction by optimizing the balance between extending lifespan and maintaining processing efficiency.
Solution Approach 2:
The wear-leveling operation is made dynamic by continuously monitoring erase cycle differences and adjusting the copy operation intensity accordingly. The system transitions between different wear-leveling intensities based on real-time block wear states, enabling the system to extend lifespan when needed while minimizing performance impact during normal operation. This dynamic approach allows the system to adaptively resolve the time-lifespan contradiction.
2Stability of the object's composition
If wear-leveling operation processes large copy amounts to quickly balance erase cycles, then erase cycle distribution is improved, but system performance and data transfer efficiency are reduced
Solution Approach 1:
The patent adjusts the copy amount parameter dynamically based on the erase cycle difference between source and destination blocks. By setting adaptive thresholds and adjusting copy amounts proportionally to the wear difference, the system achieves effective erase cycle distribution while avoiding excessive copy operations that would harm data transfer efficiency. This parameter-based control resolves the contradiction between uniformity and productivity.
Solution Approach 2:
The patent applies partial wear-leveling actions by executing copy operations only when the erase cycle difference exceeds a specific threshold. This selective approach processes only the necessary portion of wear-balancing operations, achieving sufficient erase cycle distribution uniformity without performing excessive copy operations that would degrade overall data transfer efficiency. The partial action principle allows the system to achieve adequate uniformity while preserving productivity.
3Productivity
If wear-leveling operation is executed with small copy amounts to maintain system performance, then data transfer efficiency is preserved, but the ability to quickly balance erase cycles is reduced
Solution Approach 1:
The patent implements parameter changes by adjusting copy amounts based on the magnitude of erase cycle differences. When differences are large, the system increases copy amounts to enhance wear-leveling capability; when differences are small, it reduces copy amounts to preserve system performance. This dynamic parameter adjustment resolves the contradiction between productivity and processing capability by scaling the wear-leveling intensity to match the actual wear imbalance.
4Device complexity
If wear-leveling operation uses fixed copy amount to simplify control, then device complexity is reduced, but adaptability to different wear states is reduced
Solution Approach 1:
The patent employs parameter changes to adapt the copy amount based on the current wear state of memory blocks. By monitoring erase cycle counts and adjusting the copy amount parameter dynamically, the system achieves high adaptability to different wear states while maintaining relatively simple control logic. The adaptive parameter adjustment allows the system to respond appropriately to varying wear conditions without requiring complex control mechanisms.
Data Source
AI summary
According to one embodiment, a controller, in a case where a first difference between a first number of times of erase and a second number is equal to or smaller than a second threshold, executes a copy operation in a first mode, the second number of times of erase is larger than the first number of times of erase. In a case where the first difference is larger than the second difference, the controller executes the copy operation in a second mode. A ratio of a copy amount to a cumulative data write amount in a first mode is smaller than a ratio of the copy amount to the cumulative data write amount in the second mode. The cumulative data write amount is an amount of data written to the nonvolatile memory based on write commands.