Flash Memory Block Management by Wear Level Segmentation
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Solution Overview
Problem
In nonvolatile memory systems, such as flash memory, the limited number of erase cycles for blocks leads to wear-leveling challenges, degrading performance and lifespan, as existing wear-leveling methods require significant time and resources, especially with increased block numbers.
Innovation Solution
A nonvolatile memory system and block management method that categorizes blocks by wear level and usage, grouping them to manage wear levels effectively, allowing for the selection and replacement of blocks with the lowest number of erasures, thereby optimizing block usage and extending system lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If all memory blocks are sequentially used for wear-leveling, then the lifespan of the memory system is extended, but the operation performance is degraded due to the time required for block movement and erasure
Solution Approach 1:
The patent segments the memory blocks into multiple groups based on their wear levels (e.g., first group with wear level ≤ 50%, second group with 50% < wear level ≤ 80%, third group with wear level > 80%). This segmentation allows the wear-leveling operation to focus only on specific groups rather than all blocks, reducing the number of blocks that need to be moved and erased, thus improving operation performance while still extending lifespan through targeted wear distribution.
2Quantity of substance
If the number of memory blocks is increased, then the memory capacity is increased, but the time required for selecting a replacement block for wear-leveling is increased
Solution Approach 1:
By dividing all memory blocks into multiple wear-level groups, the patent reduces the search space for selecting replacement blocks. Instead of searching through all blocks in the entire memory, the controller only needs to search within the first group (lowest wear level) to find suitable replacement blocks, significantly reducing the time required for block selection even as the total number of blocks increases.
Solution Approach 2:
The patent performs preliminary classification of blocks into wear-level groups before wear-leveling operations are needed. This preliminary action organizes blocks by their current wear status, so that when a replacement block is needed, the controller can quickly identify suitable candidates from the pre-organized first group without having to evaluate all blocks at runtime, thus reducing selection time.
3Device complexity
If blocks are managed without grouping by wear level, then the device complexity is reduced, but the wear-leveling efficiency is reduced leading to shorter lifespan
Solution Approach 1:
The patent implements a moderate level of segmentation by creating wear-level groups with simple criteria (wear level thresholds). This segmentation adds some complexity to block management but keeps it manageable through clear threshold-based classification. The benefit is significant improvement in wear-leveling efficiency, as the controller can quickly identify suitable replacement blocks from the first group, thereby extending the memory system's lifespan through more effective wear distribution.
Data Source
AI summary
A nonvolatile memory system includes a memory area including a nonvolatile memory apparatus divided into a plurality of blocks, and a controller configured to control the memory area. The controller groups the plurality of blocks of the memory area according to wear level and whether each of the plurality of blocks is in use, and manages the blocks of each group in wear level order.