Flash Memory Wear-Leveling via Logical Block Grouping
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Solution Overview
Problem
Flash memory devices have limited endurance due to repeated erasure and programming, leading to reduced capability to distinguish between states and shorter useful lifetime, especially when frequent writes occur in a small number of blocks.
Innovation Solution
A wear-leveling system and method that includes a controller and random access memory to distribute erase counts evenly across blocks, swapping blocks with higher erase counts to balance usage and extend the lifespan of flash memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If write operations are concentrated in a small number of blocks, then write speed and productivity are improved, but the endurance and reliability of the flash memory device deteriorate due to uneven wear distribution
Solution Approach 1:
The flash memory blocks are divided into multiple groups, and wear-leveling is performed at the group level rather than individual block level. This segmentation allows faster wear-leveling operations while still distributing write operations across blocks to maintain endurance, resolving the contradiction between write speed and reliability.
Solution Approach 2:
Multiple blocks within a group are treated as a unified unit for wear-leveling purposes. The wear-leveling controller manages the entire group as a single entity, combining the blocks to achieve both fast wear-leveling response and balanced wear distribution across all blocks in the group.
2Reliability
If wear-leveling is performed at the individual block level, then wear distribution is optimized for reliability, but the wear-leveling response time and complexity increase
Solution Approach 1:
By segmenting blocks into groups and performing wear-leveling at the group level, the patent reduces the number of individual wear-leveling operations required. This maintains adequate wear distribution (reliability) while significantly reducing the time and complexity associated with managing each individual block.
Solution Approach 2:
The patent applies wear-leveling at a coarser granularity (group level) rather than the finest granularity (individual block level). This partial action approach provides sufficient wear distribution to maintain reliability while avoiding the excessive time and complexity of managing every individual block.
3Productivity
If the number of erase cycles per block is increased to maximize capacity usage, then productivity is improved, but the useful lifetime of the flash memory device decreases due to exceeding endurance limits
Solution Approach 1:
The wear-leveling controller continuously monitors erase counts and dynamically adjusts the distribution of write operations across block groups. This feedback mechanism ensures that capacity is fully utilized (high productivity) while preventing any single group from exceeding endurance limits, thereby extending the useful lifetime of the flash memory device.
Solution Approach 2:
The system proactively distributes write operations across multiple block groups before any single group approaches its endurance limit. This preliminary wear-leveling action prevents premature failure and extends the overall useful lifetime of the device while maintaining high capacity utilization.
Data Source
AI summary
A memory system and corresponding method of wear-leveling are provided, the system including a controller, a random access memory in signal communication with the controller, and another memory in signal communication with the controller, the other memory comprising a plurality of groups, each group comprising a plurality of first erase units or blocks and a plurality of second blocks, wherein the controller exchanges a first block from a group with a second block in response to at least one block erase count within the group; and the method including receiving a command having a logical address, converting the logical address into a logical block number, determining a group number for a group that includes the converted logical block number, and checking whether group information comprising block erase counts for the group is loaded into random access memory, and if not, loading the group information into random access memory.