Flash Translation Layer Zone Management for SSD Data Integrity
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Solution Overview
Problem
Current flash translation layer (FTL) solutions in solid-state drives (SSDs) face challenges in efficiently maintaining data integrity during power cycles and rebuilding the logical-to-physical (LtoP) map table within a short time frame, often requiring additional components like super capacitor banks that increase cost and complexity, and may lead to reliability issues due to degradation over time.
Innovation Solution
A method and system that utilize a processor, volatile memory, and non-volatile memory to backup and reconstruct the LtoP table by dividing it into zones, where modified zones are stored in non-volatile memory when a threshold is exceeded, and quickly rebuild the table during power-on by processing flushed zone segments in reverse order, minimizing the need for additional components and ensuring data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire LtoP table is written to non-volatile memory upon power fail and read back at power on, then data integrity is preserved, but additional components (super capacitor banks) are required which increase cost and complexity
Solution Approach 1:
The LtoP table is divided into multiple zones, where only modified zones are identified and flushed to non-volatile memory. This segmentation approach allows the system to preserve data integrity for changed portions without requiring backup infrastructure for the entire table, thereby reducing the need for additional components like super capacitor banks.
Solution Approach 2:
The invention extracts and isolates only the modified portions of the LtoP table (specific zones) from the complete table. By taking out only the necessary changes and storing them in non-volatile memory, the system achieves data integrity preservation without requiring the overhead of backing up the entire table or adding extensive power backup components.
2Reliability
If the entire LtoP table is written to non-volatile memory upon power fail, then the translation table can be reconstructed, but the time required to rebuild the table increases
Solution Approach 1:
The invention extracts only the modified zones from the complete LtoP table and stores them in non-volatile memory. During power-on reconstruction, only these extracted modified zones need to be read and applied, significantly reducing the time required compared to reading and processing the entire table, thus minimizing power on time while ensuring translation table integrity.
Solution Approach 2:
The modified zones are identified and flushed to non-volatile memory in advance (before power failure). This preliminary action ensures that when power is restored, the system only needs to retrieve and apply these pre-identified modifications rather than reconstructing the entire table from scratch, thereby reducing reconstruction time.
3Reliability
If modified zones are flushed to non-volatile memory frequently, then data integrity is maintained, but write performance is impacted
Solution Approach 1:
The system dynamically adjusts the flushing behavior based on the state of the LtoP table. Instead of frequent periodic flushing, the system flushes only when specific conditions are met (when zones are modified and threshold is exceeded), making the flushing operation adaptive and conditional. This dynamic approach maintains data integrity while minimizing the frequency of flush operations to preserve write performance.
Solution Approach 2:
The invention changes the parameter of flushing frequency from a fixed high frequency to a conditional low frequency based on modification thresholds. By monitoring the number of modified zones and only flushing when the count exceeds a threshold, the system optimizes the balance between maintaining data integrity and preserving write performance, avoiding unnecessary flush operations that would degrade productivity.
Data Source
AI summary
A method of maintaining and updating a logical-to-physical (LtoP) table in a storage device including a processor, a volatile memory, and a non-volatile memory, the storage device being in communication with a host, the method including receiving, by the processor, data for storing at a physical address in the non-volatile memory, the data being associated with a logical address of the host, storing, by the processor, the physical address in a first LtoP zone of a plurality of LtoP zones of the LtoP table, the LtoP table being stored in the volatile memory, adding, by the processor, the first LtoP zone to a list of modified zones, and storing, by the processor, a second LtoP zone of the plurality of LtoP zones in the non-volatile memory when a size of the list of modified zones exceeds a threshold.