Flash Memory Read-Disturb Prevention via Data Migration
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Solution Overview
Problem
Flash memory devices, particularly multi-level cell (MLC) flash memories, experience data loss or corruption due to 'read-disturb' errors when data is repeatedly read, leading to storage reliability issues.
Innovation Solution
A method is introduced to prevent read-disturb by recording read times using a read times table and transferring data from heavily read blocks to spare blocks when read times exceed a predetermined value, ensuring accurate data retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is repeatedly read from flash memory blocks, then data access frequency increases, but read-disturb errors occur causing data loss or corruption
Solution Approach 1:
The patent implements preliminary action by proactively monitoring read times of data blocks and transferring data before read-disturb errors occur. The controller records read times for each block and compares against a threshold, moving frequently read data to new blocks before degradation happens, thus preventing data loss while maintaining high access frequency.
Solution Approach 2:
The patent applies copying by creating duplicate copies of frequently read data blocks. When a block's read time exceeds the threshold, the controller copies the data to a new block and updates the mapping, allowing the original block to be reused. This copying mechanism preserves data integrity while supporting continuous high-frequency access.
2Measurement precision
If read times table is maintained to track block access, then read-disturb prevention accuracy improves, but controller complexity increases
Solution Approach 1:
The patent implements self-service by having the controller automatically update and manage the read times table without external intervention. The controller increments read time counters for each accessed block and autonomously determines when transfer is needed, reducing the need for complex external management systems while maintaining precise tracking.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the read time threshold based on memory characteristics and usage patterns. The controller can modify the threshold parameter to optimize between prevention accuracy and operational complexity, allowing flexible adaptation without restructuring the entire control system.
Data Source
AI summary
A method for preventing read-disturb happened in non-volatile memory and a controller thereof are disclosed. The non-volatile memory includes a plurality of blocks, and each block includes a plurality of pages. The method includes storing a program code executed by a controller of the non-volatile memory storage device for controlling the non-volatile memory storage device into at least a first block of the blocks; and copying the program code stored in the first block into at least a second block of the blocks when power is supplied to the non-volatile memory storage device.