Memory Controller Wear-Leveling via Cell Degradation Assessment
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Solution Overview
Problem
Current storage devices face challenges in maintaining optimal wear-leveling performance, leading to inefficient data distribution and degradation across memory blocks, which affects overall storage device reliability and longevity.
Innovation Solution
A memory controller is introduced that utilizes reference voltages to read and assess memory cell degradation, performing error correction and implementing a read reclaim operation to redistribute data based on degradation and error rates, thereby optimizing wear-leveling across memory blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wear-leveling is performed without monitoring memory cell degradation, then data distribution is simplified, but storage device reliability deteriorates due to inefficient data distribution
Solution Approach 1:
The system performs preliminary read operations to assess memory cell degradation before data redistribution is needed. By proactively evaluating the state of memory cells through reference voltage comparisons, the system prepares wear-leveling actions in advance, preventing potential failures before they occur and improving reliability without waiting for degradation to become critical.
Solution Approach 2:
The system establishes a feedback loop where memory cell degradation is continuously monitored through read operations, and this information feeds back into the wear-leveling decision-making process. The cell state determiner provides real-time status information about memory block conditions, enabling dynamic adjustment of data distribution strategies to optimize reliability based on actual degradation trends.
2Measurement precision
If read operations are performed frequently to monitor degradation, then memory cell degradation assessment improves, but wear-leveling performance deteriorates due to increased read count
Solution Approach 1:
Instead of performing complete read operations on all memory cells, the system uses partial read operations sampling specific memory cells to assess degradation. By using reference voltages to compare against expected values, the system achieves sufficient degradation measurement precision without the excessive action of reading every cell, thus balancing measurement accuracy with wear-leveling performance.
3Reliability
If data redistribution is performed based on single threshold criteria, then wear-leveling is simplified, but reliability deteriorates due to insufficient consideration of multiple degradation factors
Solution Approach 1:
The system applies different evaluation criteria and thresholds to different memory blocks based on their individual degradation characteristics. Rather than using a uniform threshold for all blocks, the wear-leveling controller assesses each block's specific state through read operations and applies appropriate redistribution strategies locally, improving reliability by tailoring control actions to actual block conditions.
Solution Approach 2:
The wear-leveling system dynamically adjusts redistribution strategies based on real-time degradation monitoring. The controller continuously evaluates memory block states and adapts its data redistribution actions accordingly, transitioning from static threshold-based control to dynamic, condition-based control that responds to changing degradation patterns and optimizes reliability under varying conditions.
Data Source
AI summary
A memory controller having improved wear-leveling performance controls a memory device including a plurality of memory blocks. The memory controller includes a read operation controller, a cell state determiner, and a read reclaim controller. The read operation controller controls the memory device to read selected memory cells of a first block among the plurality of memory blocks by using at least one reference voltage. The cell state determiner compares a number of memory cells among the selected memory cells that are read as first memory cell with a reference number corresponding to the at least one reference voltage, and generates cell state information indicating a memory cell degradation degree corresponding to at least one state. The read claim controller controls the memory device to copy data stored in the first block to a second block, based on a comparison between the memory cell degradation degree with a threshold degradation degree.