SSD Controller Format Handling via Volatile Memory Copying
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Solution Overview
Problem
Solid-state drives (SSDs) face increased latency and write amplification during formatting due to the large size of the logical-to-physical mapping table, leading to inefficiencies and potential errors from lost updates during power loss.
Innovation Solution
The method involves using invalid addresses to unmapping and copying a dummy region across the SSD's volatile memory, reducing the need for frequent writes to non-volatile memory by using a copy command instead of a special update command, and managing deallocate flags to minimize write amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the mapping table is loaded into volatile memory for fast access during formatting, then access speed is improved, but the time required to write the large mapping table back to non-volatile memory increases latency
Solution Approach 1:
The mapping table is divided into multiple regions, and only the regions that need to be updated during formatting are written back to non-volatile memory, rather than writing the entire large mapping table. This segmentation reduces the total write time and latency while maintaining fast access to the necessary portions in volatile memory.
2Reliability
If the entire mapping table is written to non-volatile memory during formatting, then data integrity is ensured, but write amplification increases due to the large size of the mapping table
Solution Approach 1:
Only the necessary portions of the mapping table that require updates during formatting are extracted and written to non-volatile memory, rather than writing the entire mapping table. This extraction approach ensures data integrity for the updated regions while minimizing write amplification by excluding unnecessary data from the write operation.
3Loss of information
If the mapping table is frequently updated during formatting operations, then address information is kept current, but the large size of the mapping table leads to increased write amplification and latency
Solution Approach 1:
The mapping table is segmented into regions, and updates are performed on a per-region basis during formatting operations. This allows address information to be kept current for only the necessary regions without the overhead of updating the entire large mapping table, thereby reducing write latency while maintaining address information accuracy.
Data Source
AI summary
A method performed by a controller of a solid-state drive (SSD) comprising receiving a command from a host, the command identifying a namespace in a non-volatile semiconductor memory device of the SSD to be formatted, identifying a plurality of regions in the non-volatile semiconductor memory device corresponding to the namespace, unmapping a dummy region in a volatile semiconductor memory device of the SSD using invalid addresses, and copying the invalidated dummy region to each region of the plurality of regions of the namespace.