Flash Memory Wear-Leveling via Minimal Erase Count Tracking
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Solution Overview
Problem
The static wear-leveling algorithm in flash memory devices is inefficient, leading to uneven erase count distribution across physical blocks, causing some blocks to be prematurely damaged while others are underutilized, due to frequent data migration and poor selection strategies, which reduces the lifetime of flash memory.
Innovation Solution
A data retention method that maintains a minimum erase count and number for blocks in a flash memory array, where the controller manages erase operations to balance erase counts by scanning only when necessary, storing these values to prevent loss during power outages, and selectively migrates data based on erase count thresholds to optimize wear-leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If static wear-leveling algorithm is implemented to balance erase counts, then flash memory lifetime is improved, but hardware overhead increases due to frequent scanning
Solution Approach 1:
The controller pre-calculates and stores the minimum erase count and minimum erase number before power-off. This preliminary action allows the wear-leveling algorithm to resume efficiently after power restoration without requiring extensive scanning, thus extending flash memory lifetime while reducing hardware overhead.
Solution Approach 2:
The patent extracts and stores only the critical parameters (minimum erase count and minimum erase number) from the flash memory array, rather than scanning the entire array. This extraction approach maintains wear-leveling effectiveness while significantly reducing the scanning overhead and hardware complexity.
2Reliability
If minimum erase count and number are stored in flash memory array, then data retention during power loss is improved, but storage space is consumed
Solution Approach 1:
The patent stores the minimum erase count and minimum erase number in a specific localized region of the flash memory array rather than distributing storage requirements across the entire array. This localized storage approach ensures data retention during power loss while consuming minimal storage space.
3Manufacturing precision
If frequent scanning is performed to maintain wear-leveling, then erase count distribution is optimized, but processing time increases
Solution Approach 1:
The patent implements periodic wear-leveling operations triggered by power events rather than continuous scanning. The controller performs wear-leveling maintenance at periodic intervals based on power cycles, using the stored minimum erase count and number to guide operations. This periodic approach maintains erase count distribution uniformity while minimizing processing time loss.
Data Source
AI summary
A storage device includes a flash memory array and a controller. The flash memory array includes a plurality of blocks. A minimal erase number of blocks have a minimal erase count in the plurality of blocks. When one of the minimal erase number of blocks is erased, the controller subtracts 1 from the minimal erase number.