Memory Controller SPO Reclaim Strategy
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Solution Overview
Problem
Memory systems face data retention issues due to sudden power off (SPO) events, leading to uncorrectable errors and data damage, as reclaim operations are not performed at the proper time, especially when SPO occurs before read counts can be updated.
Innovation Solution
A controller that selects a read group based on the occurrence number of SPO using a round robin scheme and performs a reclaim operation on data with fewer error bits than a predetermined threshold, ensuring data integrity even during repeated SPO events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If reclaim operation is not performed after sudden power off, then power consumption is reduced and operation speed is maintained, but data retention time decreases and uncorrectable errors increase
Solution Approach 1:
The controller performs reclaim operations proactively after detecting sudden power off events, before data corruption becomes irreversible. By identifying affected read groups and executing reclaim operations in advance, the system prevents data retention degradation rather than reacting to errors after they occur.
Solution Approach 2:
The controller implements a feedback mechanism that monitors power off events and uses this information to determine when reclaim operations are needed. The controller counts sudden power off occurrences and selectively performs reclaim operations on affected read groups, creating a closed-loop system that adapts to actual power events.
2Reliability
If reclaim operation is performed on all data after sudden power off, then data integrity is improved, but processing time increases and productivity decreases
Solution Approach 1:
The controller divides the memory space into multiple read groups and selectively performs reclaim operations only on specific segments (read groups) that were affected by sudden power off events. This segmentation allows the system to maintain data integrity for affected regions while avoiding unnecessary processing of unaffected data, thus preserving overall processing productivity.
Solution Approach 2:
Instead of performing reclaim operations on all data, the controller applies partial action by targeting only the necessary subset of read groups that experienced power off events. This selective approach provides sufficient error correction for affected data while minimizing the processing overhead and maintaining system productivity.
3Measurement precision
If read count is updated before sudden power off, then reclaim operation timing is accurate, but system complexity increases and ease of operation decreases
Solution Approach 1:
The controller updates read counts and identifies affected read groups as a preliminary step immediately after detecting sudden power off events. By performing this identification in advance, the system establishes accurate timing information for subsequent reclaim operations without requiring continuous monitoring or complex real-time decision-making mechanisms.
Data Source
AI summary
An operating method of a controller, the operating method comprising: reading first data stored in a first read group selected among read groups of a memory device when a sudden power off (SPO) occurs and then power is on; identifying the number of error bit data in each of the first data; and performing a reclaim operation to each of the first data based on the number of error bit data in each of the first data.