SSD Data Logs for Garbage Collection Read Failure Recovery
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Solution Overview
Problem
Solid State Drives (SSDs) face challenges with unpredictable read latency and high uncorrectable bit error rates (UBER) due to repetitive ECC decoding failures and heroic data recovery procedures, which degrade reliability and performance.
Innovation Solution
Implementing data tracking logs to record previous locations of data during garbage collection operations, allowing retrieval from older locations when current reads fail, thereby reducing UBER and improving read latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ECC decoding and heroic data recovery procedures are used, then data integrity is maintained, but read latency increases and reliability decreases due to unpredictable failures
Solution Approach 1:
The patent maintains data logs that record previous physical locations of data before garbage collection operations. When a read failure occurs, the system can immediately retrieve data from the logged previous location without performing complex heroic recovery procedures, thus reducing read latency while maintaining data integrity
Solution Approach 2:
The data log acts as an intermediary structure that stores historical location information. Instead of directly attempting heroic recovery when a read fails, the system first checks the data log to find a previous valid location, simplifying the recovery process and reducing time loss
2Reliability
If heroic data recovery procedures are implemented, then uncorrectable bit error rate decreases, but device complexity and operational complexity increase
Solution Approach 1:
The patent extracts the location tracking function from the complex heroic recovery process by maintaining separate data logs that record previous physical locations. This separates the simple location retrieval task from the complex error recovery procedures, reducing overall system complexity while improving UBER
Solution Approach 2:
The system creates a copy of location information in data logs before garbage collection operations. This copy allows the system to quickly retrieve previous locations without needing to perform complex analysis during recovery, simplifying the overall process while reducing uncorrectable bit errors
3Productivity
If garbage collection operations are performed frequently, then storage efficiency improves, but data location tracking becomes more complex and read failures increase
Solution Approach 1:
The system performs preliminary recording of data locations in data logs before garbage collection operations occur. This preliminary action ensures that even with frequent garbage collection, the location information is already captured and can be quickly retrieved if needed, maintaining storage efficiency without increasing tracking complexity
Data Source
AI summary
In some implementations, a controller may detect a failure associated with data obtained, using a first physical address, from a current physical location of a non-volatile memory device. The controller may determine, based on detecting the failure, a virtual block number based on the first physical address. The controller may determine that the virtual block number identifies a garbage collection block. The controller may determine a virtual wordline of the garbage collection block. The controller may obtain, from the virtual wordline, a data log that identifies a second physical address for a previous physical location of the data. The controller may obtain, using the second physical address, the data from the previous physical location.