Storage Device Journal Replay Segmentation
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Solution Overview
Problem
Storage devices with nonvolatile memory face data loss during power events due to the volatility of meta data, such as address mapping tables, which are crucial for data integrity and recovery.
Innovation Solution
Implementing a storage device with a nonvolatile memory that includes a main meta data area and a journal area, where the controller updates and stores page mapping entries in the journal area and segments in the main meta data area based on priorities, ensuring data coherence and reducing the time and cost of journal replay during recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller stores the entire address mapping table in the nonvolatile memory as a single unit, then data integrity is ensured, but the journal replay time and cost increase significantly
Solution Approach 1:
The patent divides the address mapping table into multiple segments, each stored as a separate entry in the journal area. During journal replay, only the segments that were updated need to be recovered, rather than replaying the entire table. This segmentation reduces the journal replay time and computational cost while maintaining data integrity through selective recovery of only necessary segments.
2Productivity
If the controller stores meta data in the volatile memory for fast access, then write speed improves, but data loss occurs during power events
Solution Approach 1:
The controller preliminarily stores updated page mapping entries (meta data) in the journal area of the nonvolatile memory before completing the write operation. This preliminary action ensures that even if a power event occurs, the critical meta data is already preserved in nonvolatile storage, preventing data loss while maintaining fast write performance through volatile memory caching.
3Loss of time
If the controller divides the address mapping table into many small segments, then journal replay efficiency improves, but the device complexity increases
Solution Approach 1:
The journal area serves multiple functions: it acts as both a transaction log for tracking updates and a segmented storage structure for the address mapping table. This multi-functionality allows the system to achieve efficient journal replay through segmentation without requiring separate complex structures, as the journal area itself provides both logging and segmented storage capabilities.
Data Source
AI summary
A storage device includes a nonvolatile memory including a main meta data area and a journal area, and a controller. The controller updates an address mapping table including a plurality of page mapping entries divided into a plurality of segments by executing a flash translation layer (FTL) stored in a working memory, stores updated page mapping entries of the plurality of page mapping entries in the journal area as journal data, and stores the plurality of segments, each having a size smaller than a physical page of the nonvolatile memory, in the main meta data area.