Storage System Predictive Read Threshold Adjustment
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Solution Overview
Problem
Non-volatile memory systems, such as NAND flash, face impaired read-back reliability due to increased cell density, leading to performance degradation and longer read access times, with existing solutions failing to effectively address these issues.
Innovation Solution
A predictive adjustment mechanism using a control processor to read user data with a read threshold, determine the appropriate threshold adjustment range by analyzing a 1 and 0 counter, and select an adjusted read threshold to correct user data, thereby minimizing read errors and improving system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cell density is increased to reduce cost per gigabyte, then storage capacity is improved, but read-back reliability deteriorates
Solution Approach 1:
The system performs preliminary actions by proactively adjusting read thresholds before read errors occur. The control processor monitors 1 and 0 counters during read operations and adjusts thresholds in advance to prevent reliability degradation, rather than reacting after errors occur. This preliminary adjustment maintains read-back reliability despite increased cell density.
Solution Approach 2:
The invention changes the read threshold parameter dynamically based on monitored error patterns. By adjusting the voltage threshold used to read data from memory cells, the system adapts to changes in cell characteristics caused by high density packing, thereby maintaining reliable read operations despite increased storage capacity.
2Reliability
If read threshold adjustments are performed reactively, then data reliability can be maintained, but read access time increases
Solution Approach 1:
The control processor performs preliminary threshold adjustments by monitoring 1 and 0 counters and proactively modifying read thresholds before significant read errors occur. This prevents the need for time-consuming reactive error recovery retries, thereby maintaining both data reliability and fast read access times.
Solution Approach 2:
The system implements feedback by continuously monitoring 1 and 0 counters during read operations and using this information to adjust read thresholds. This closed-loop control enables the system to maintain optimal read performance and reliability without requiring multiple retry attempts, thus minimizing read access time loss.
3Measurement precision
If multiple read retries are performed to correct errors, then data accuracy is improved, but system performance deteriorates
Solution Approach 1:
The system performs preliminary threshold adjustments to prevent read errors before they occur, eliminating the need for multiple read retries. By proactively adapting read thresholds based on monitored error patterns, the system maintains high data accuracy while avoiding the performance penalty associated with repeated read attempts.
Solution Approach 2:
The feedback mechanism using 1 and 0 counters enables the system to detect and correct threshold drift proactively. This continuous monitoring and adjustment prevents the accumulation of read errors that would otherwise require multiple retries, thereby maintaining both data accuracy and system performance.
Data Source
AI summary
A storage system includes: a control processor, configured to: read user data with a read threshold, determine which threshold adjustment range has been activated by reading a 1 and 0 counter, select an adjusted read threshold, based on the threshold adjustment range, to reread the user data in a physical block using the adjusted read threshold to correct the user data; and reading the user data in the physical block using the adjusted read threshold selected from the threshold adjustment range.