Storage Controller Read Reclaim Latency Management
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Solution Overview
Problem
Current storage devices face challenges in maintaining operation speed and data reliability due to increasing error bits in nonvolatile memory blocks, leading to latency issues during read operations.
Innovation Solution
A storage device with a controller that performs read reclaim operations by migrating valid data from error-prone memory blocks to other blocks through multiple migration operations, dynamically adjusting the amount of data migrated based on the reliability of the source block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is migrated from error-prone memory blocks to other blocks, then data reliability is improved, but operation speed deteriorates due to increased latency
Solution Approach 1:
The migration operation is divided into multiple segments or phases. The controller performs read reclaim operations in stages, migrating data from error-prone blocks to healthy blocks incrementally rather than all at once, thereby reducing the impact on operation speed while maintaining data reliability
Solution Approach 2:
The controller proactively identifies error-prone memory blocks before they fail completely and performs read reclaim operations in advance. By detecting blocks with increasing error bits and migrating data beforehand, the system prevents future read failures without causing latency when actually needed
2Reliability
If read reclaim is performed frequently to maintain data reliability, then data reliability is improved, but productivity deteriorates due to increased migration operations
Solution Approach 1:
The controller continuously monitors the error bit count in memory blocks and uses this feedback to dynamically adjust read reclaim operations. When error bits exceed a threshold, read reclaim is triggered; when errors are low, operations are minimized, optimizing the balance between reliability and productivity
Solution Approach 2:
The system changes operational parameters based on memory block condition. The read reclaim frequency and data migration amount are adjusted according to the error rate and reliability status of source blocks, allowing the system to maintain reliability only when necessary rather than performing constant migrations
Data Source
AI summary
A storage device is provided. The storage device includes a nonvolatile memory device including memory blocks, and a controller configured to perform write, read and erase operations with respect to a selected memory block from among the memory blocks. If the number of error bits is greater than a critical value in a read operation with respect to the selected memory block, the controller is configured to perform a read reclaim of migrating valid data stored in the selected memory block to another memory block through at least two migration operations. In the read reclaim, the controller is configured to adjust an amount of data migrated in one migration operation.