Buffer Memory Read Reclaim for Flash Data Integrity
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Solution Overview
Problem
Flash memory devices face issues with data loss and delayed read operations due to read disturbance errors, which can lead to uncorrectable errors and decreased storage device quality, especially when read reclaim operations are delayed.
Innovation Solution
A storage device with a nonvolatile memory, memory controller, and buffer memory is implemented, where the memory controller identifies target data for read reclaim, copies it to another memory block, and communicates specified data from the buffer memory to a host device before erasing, thereby preventing data loss and reducing read operation delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If read reclaim operation is delayed, then data loss risk increases and uncorrectable errors occur, but read operation speed decreases and response time is delayed
Solution Approach 1:
The patent applies preliminary action by performing read reclaim operations proactively before uncorrectable errors occur. The memory controller identifies memory blocks with high read disturbance risk and copies data to new blocks in advance, preventing data loss while maintaining read performance through buffer memory
Solution Approach 2:
The buffer memory serves as an intermediary component that decouples the read reclaim operation from the read request path. Data can be served from the buffer memory during read reclaim operations, preventing read speed degradation while still performing the necessary data copying and erasure operations
2Reliability
If read reclaim operation is performed frequently, then data loss is prevented, but read operation speed decreases due to operation overhead
Solution Approach 1:
The patent applies partial action by selectively performing read reclaim operations only on memory blocks that exhibit high read disturbance characteristics. The memory controller identifies specific blocks based on read count thresholds or error patterns, rather than performing reclaim on all blocks, thus reducing overall operation overhead while maintaining data integrity for at-risk data
Solution Approach 2:
The system uses self-service by monitoring its own read patterns and automatically identifying memory blocks that require read reclaim operations. The memory controller tracks read counts and error rates, autonomously determining which blocks need data copying without external intervention, optimizing the balance between reliability and performance
Data Source
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AI summary
Described is a storage device includes a nonvolatile memory device, a memory controller, and a buffer memory. The memory controller determines a first memory block of the nonvolatile memory device, which is targeted for a read reclaim operation, and reads target data from a target area of the first memory block. The target data are stored in the buffer memory. The memory controller reads at least a portion of the target data stored in the buffer memory in response to a read request corresponding to at least a portion of the target area.