Memory Controller Wear Leveling Adaptation
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Solution Overview
Problem
Existing memory systems, such as SSDs with NAND flash memory, face inefficiencies in wear leveling, particularly in access patterns with low static data ratios, where dynamic data is unnecessarily rewritten, leading to unbalanced erasure cycles and shortened device life.
Innovation Solution
A memory system that dynamically determines whether to activate static wear leveling (SWL) based on the static data ratio and erasure differences between blocks, selectively rewriting data to balance erasure cycles, especially in access patterns with high static data ratios, thereby optimizing wear leveling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static wear leveling (SWL) is executed for all blocks including those with dynamic data, then the number of erasures is leveled across blocks, but unnecessary rewrites occur in low static data ratio patterns leading to increased write amplification
Solution Approach 1:
The patent applies local quality by differentiating wear leveling treatment based on data characteristics. It identifies blocks containing static data versus dynamic data and applies SWL selectively only to blocks with static data, rather than uniformly to all blocks. This localized approach prevents unnecessary rewrites of dynamic data while maintaining erasure leveling where it provides benefit.
Solution Approach 2:
The patent implements dynamics by making the wear leveling process adaptive to changing data patterns. It continuously monitors the static data ratio in each block and adjusts the wear leveling execution accordingly. When the static data ratio falls below a threshold, SWL is suspended for that block, allowing the system to respond dynamically to access patterns rather than applying a static wear leveling policy.
2Productivity
If SWL is suspended in low static data ratio patterns, then unnecessary rewrites are suppressed, but erasure cycles become unbalanced leading to premature block failure
Solution Approach 1:
The patent employs feedback by continuously monitoring the static data ratio in each block and using this information to control SWL execution. The system measures the proportion of static data, compares it against a predetermined threshold, and adjusts wear leveling behavior accordingly. This closed-loop feedback mechanism ensures SWL is activated when beneficial and suspended when harmful, balancing productivity and reliability.
Solution Approach 2:
The patent applies parameter changes by using the static data ratio as a control parameter to determine SWL execution. Rather than using a fixed wear leveling policy, the system changes its behavior based on the measured static data ratio parameter. When this parameter exceeds the threshold, SWL is enabled; when it falls below, SWL is suspended, allowing adaptive optimization of wear leveling.
3Productivity
If the controller monitors static data ratio and erasure differences to determine SWL execution, then wear leveling is optimized, but control complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the wear leveling control into distinct functional modules: one for monitoring static data ratio, another for tracking erasure cycle differences between blocks, and a third for making SWL execution decisions. This modular segmentation of control logic makes the complex decision-making process more manageable and implementable within the controller architecture.
Data Source
AI summary
A controller of a memory system according to an embodiment manages, for each of a plurality of blocks, first information indicating whether a corresponding block is in use which indicates a state where the data is stored, second information indicating the number of erasures, and third information indicating a waiting time until next erasure. The controller executes first sequential write received from a host, and determines whether to execute processing of leveling the number of erasures for each of the plurality of blocks based on a first difference, a second difference, and a third difference when executing second sequential write received from the host.