Wear Leveling in Solid State Devices Using Grouped Memory Blocks
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Solution Overview
Problem
Current flash memory devices face limitations in wear leveling due to the need for large memory structures to track wear counts, which consume significant resources and are inefficient in identifying memory blocks for garbage collection operations.
Innovation Solution
A memory-efficient mechanism is implemented using a wear count table to identify memory blocks within the bottom p% of all wear counts, allowing the memory controller to select blocks for garbage collection, thereby leveling wear across memory blocks and reducing memory usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wear leveling methods are used to track wear counts of memory blocks, then wear leveling can be achieved, but large memory structures are required to track wear counts, consuming significant resources
Solution Approach 1:
The patent divides the memory blocks into multiple groups based on their wear counts. Instead of tracking every individual block's wear count in detail, the system segments blocks into groups (e.g., first group with lower wear counts, second group with higher wear counts). This segmentation reduces the memory required for tracking while still enabling effective wear leveling by selecting from appropriate groups.
Solution Approach 2:
The patent changes the parameter being tracked from individual block wear counts to group-based wear characteristics. By maintaining wear count information at the group level rather than individual block level, and by using thresholds to differentiate groups, the system reduces memory consumption while preserving the essential wear leveling functionality.
2Reliability
If memory blocks are selected for garbage collection based on wear count, then wear leveling is improved, but efficient identification of suitable blocks requires complex tracking structures
Solution Approach 1:
The patent segments memory blocks into groups based on wear count thresholds. The first group contains blocks with wear counts below a first threshold, and the second group contains blocks with wear counts above the first threshold and below a second threshold. This segmentation simplifies the identification process for garbage collection by providing clear categories rather than requiring complex individual block analysis.
Solution Approach 2:
The patent applies different selection criteria to different groups of memory blocks. When selecting blocks for garbage collection, the system preferentially selects from the first group (lower wear counts) to preserve higher-endurance blocks for future writes. This local quality approach optimizes wear leveling by tailoring selection strategy to the specific characteristics of each group.
3Measurement precision
If wear count tracking is implemented for all memory blocks, then accurate wear leveling can be achieved, but memory resources are significantly consumed
Solution Approach 1:
The patent implements wear count tracking at the group level rather than maintaining detailed records for every individual memory block. By segmenting blocks into groups based on wear thresholds and tracking aggregate or representative wear information for each group, the system achieves sufficient measurement precision for wear leveling while dramatically reducing memory consumption.
Solution Approach 2:
The patent tracks wear count information partially - specifically for groups of blocks rather than every individual block. This partial tracking approach provides sufficient information for effective wear leveling decisions without the excessive memory consumption of complete individual block tracking. The system uses thresholds to determine when partial tracking is sufficient.
Data Source
AI summary
Embodiments of the present disclosure provide a memory-efficient mechanism for identifying memory blocks with a low wear count. More particularly, embodiments of the present disclosure provide a mechanism for identifying a memory block whose wear count is within the bottom p % of all wear counts associated with memory blocks in a storage system. If a memory controller performs the garbage collection operation on a memory block whose wear count is within the bottom p % of all wear counts, then the memory controller is expected to utilize the remaining memory blocks (e.g., memory blocks whose wear count is within the upper (100-p) % of all wear counts) efficiently and level the wear count of at least the remaining memory blocks.