NAND Flash Patrol Process Optimization
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Solution Overview
Problem
Solid-state drives (SSDs) with NAND flash memory experience significant time consumption during the patrol process, which involves reading and verifying data across all storage areas, due to the degradation of data over time or from read/write operations, especially in peripheral areas.
Innovation Solution
A memory system with a controller circuit that executes a patrol process by reading and verifying data in units of pages across multiple physical blocks in parallel, prioritizing media block addresses over page addresses to efficiently complete the patrol process, thereby reducing unnecessary data verification in high-quality correlation areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the patrol process reads and verifies data across all storage areas in sequential order, then data integrity is ensured, but the patrol process takes a substantial amount of time to complete
Solution Approach 1:
The patrol process is segmented into two distinct phases: a first patrol process that reads data from all storage areas to ensure comprehensive coverage and data integrity, and a second patrol process that verifies only specific storage areas suspected of degradation. This segmentation allows the system to maintain reliability while reducing the time required for complete verification.
Solution Approach 2:
The system performs a complete read of all storage areas in the first patrol process, then performs selective verification only in areas showing degradation signs in the second patrol process. This partial verification approach reduces overall patrol time while maintaining data integrity through the initial comprehensive read.
2Reliability
If the patrol process verifies all pages in all physical blocks, then complete data verification is achieved, but the patrol process efficiency is reduced
Solution Approach 1:
The patrol process applies different verification strategies to different storage areas based on their quality characteristics. Storage areas identified as having low quality correlation undergo verification in the first patrol process, while high quality correlation areas are verified in the second patrol process. This localized quality-based approach improves overall patrol efficiency while maintaining verification completeness.
Solution Approach 2:
The system performs preliminary identification of storage area quality characteristics before executing the verification pattern. By pre-categorizing storage areas into high and low quality correlation groups, the system can optimize the verification sequence and reduce unnecessary verification operations, thereby improving patrol process efficiency.
3Reliability
If the patrol process executes verification in units of pages across multiple physical blocks, then data integrity is maintained, but the process consumes significant time
Solution Approach 1:
The verification process is segmented into two patrol processes with different scopes. The first patrol process verifies data in units of pages across all physical blocks to ensure comprehensive coverage. The second patrol process performs targeted verification only in specific storage areas, reducing the overall verification duration while maintaining data integrity through the initial comprehensive verification.
Data Source
AI summary
A memory system includes a nonvolatile memory device and a controller circuit. The nonvolatile memory device includes a plurality of physical blocks, each including a storage area which is accessible in units of pages. The controller circuit is configured to control reading and writing of data which are performed on the plurality of physical blocks in units of pages. The controller circuit is also configured to execute a first process on the plurality of physical blocks by performing a second process of reading and a third process of data verification on a first page across each of the plurality of physical blocks and then performing the second process of reading and the third process of data verification on a second page across each of the plurality of physical blocks.