SSD LBA Table Recovery via Circular Buffer Segmentation
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Solution Overview
Problem
Sudden power loss in memory systems, such as solid state drives (SSDs), results in data loss due to the volatility of logical block addressing (LBA) tables, and existing recovery methods are time-consuming and inefficient, particularly in rebuilding the LBA table and performing garbage collection.
Innovation Solution
The implementation of a memory system with a controller that determines the most recently saved, previous, and least recently saved sections of the LBA table, reads and updates entries from open and closed super blocks, and uses bitmaps to reduce the number of updates and scanning time during recovery, thereby accelerating the rebuilding process and improving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing recovery methods are used to rebuild the LBA table after sudden power loss, then data integrity is restored, but the recovery time is excessively long and system performance deteriorates
Solution Approach 1:
The system performs preliminary actions by maintaining a circular buffer that continuously stores backup sections of the LBA table in volatile memory during normal operation. When sudden power loss occurs, the controller can immediately restore the LBA table from these pre-stored backups without time-consuming reconstruction, thus resolving the contradiction between data integrity and recovery time
Solution Approach 2:
The LBA table is segmented into multiple sections that are distributed across different super blocks. The circular buffer stores these sections in an organized manner, allowing the controller to selectively restore only the necessary sections after power loss, reducing overall recovery time while ensuring data integrity
2Reliability
If the controller reads and updates all super blocks to rebuild the LBA table, then complete data recovery is achieved, but the number of I/O operations increases and performance decreases
Solution Approach 1:
The invention extracts only the essential LBA table sections needed for recovery from the circular buffer, rather than reading and processing all super blocks. The controller identifies and restores only the specific sections that were present in the buffer at the time of power loss, significantly reducing I/O operations while maintaining complete data recovery
Solution Approach 2:
The system performs partial action by restoring only the LBA table sections that are available in the circular buffer backup, rather than attempting to reconstruct the entire table from all super blocks. This partial restoration is sufficient to regain system functionality and maintain productivity
3Loss of information
If the LBA table is frequently updated to reflect current data state, then data accuracy is maintained, but write amplification increases and memory endurance decreases
Solution Approach 1:
The circular buffer pre-stores LBA table sections during normal operation, creating a backup mechanism that eliminates the need for frequent writes to non-volatile memory for recovery purposes. This preliminary buffering action maintains data accuracy while reducing write amplification and preserving memory endurance
Solution Approach 2:
Instead of frequently writing the complete LBA table to non-volatile memory, the system creates copies of essential LBA sections in the circular buffer in volatile memory. These copies are used for recovery, reducing the need for repetitive writes to memory cells and thereby extending memory endurance while maintaining data accuracy
Data Source
AI summary
Methods may include after a power loss, determining a most recently saved section of a logical block addressing (LBA) table, a previous section saved prior to the most recently saved section of the LBA table, and a least recently saved section of the LBA table, reading an open super block and updating entries in the LBA table from the most recently saved section through to the least recently saved section, reading a newest closed super block from a plurality of closed super blocks and updating entries in the LBA table from the previous section saved prior to the most recently saved section through to the least recently saved section, and reading an oldest super block and updating entries in the LBA table in the least recently saved section.