SSD Power Fail Saving Mode Using pSLC Metadata and Dummy Pages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing solid state drives (SSDs) face challenges in minimizing the time required to write essential data to non-volatile memory after a power failure, which increases the size and cost of the backup power supply needed for a graceful shutdown.
Innovation Solution
The SSD employs a power fail saving mode that uses a pseudo Single Level Cell (pSLC) mode for system metadata and a modified Multi-Level Cell (MLC) write procedure with dummy pages to reduce the holdup time, allowing data to be written in a more efficient and error-protected manner, eliminating the need to write complete blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written to flash memory in complete blocks in MLC mode, then data integrity is improved, but write speed deteriorates
Solution Approach 1:
The patent segments the flash memory block into two distinct regions: a pSLC region for writing critical metadata and a MLC region for normal data storage. This segmentation allows the critical metadata to be written faster in pSLC mode while maintaining data integrity requirements, resolving the contradiction between write speed and data integrity for power fail protection.
Solution Approach 2:
The patent applies different quality standards to different parts of the flash memory system. The pSLC region uses single-level cell characteristics (higher reliability, faster write) specifically for metadata, while the MLC region maintains multi-level cell characteristics for bulk data storage. This local differentiation optimizes both speed and integrity where needed.
2Duration of action of moving object
If a larger backup power supply is provided, then holdup time is improved, but device size and cost worsen
Solution Approach 1:
The patent performs preliminary action by writing critical metadata to the pSLC region before a power failure occurs. This pre-positioning of essential data in the faster, more reliable pSLC region reduces the time window during which backup power is needed, thereby reducing the required holdup time and allowing for a smaller backup power supply.
Solution Approach 2:
The pSLC region acts as an intermediary buffer between the host interface and the MLC flash memory. By using this intermediate storage layer for critical metadata, the system reduces the time required to ensure data integrity during power failures, thereby reducing backup power requirements.
3Productivity
If pSLC mode is used for metadata, then write speed is improved, but storage capacity is reduced
Solution Approach 1:
The patent segments the flash memory into pSLC and MLC regions, allocating only the portion needed for metadata to pSLC mode. This segmentation allows the system to gain the write speed benefits of pSLC for critical operations while preserving the high-capacity MLC region for bulk data storage, thus minimizing the capacity trade-off.
Data Source
AI summary
A solid state drive has a power failure savings mode that permits a reduction in holdup time for a temporary backup power supply. The solid state drive stores data in a multi-level cell (MLC) mode. In a power fail saving mode system metadata is written in a pseudo Single Level Cell (pSLC) mode. In the normal operating mode page writes are performed in complete blocks. In the power fail save saving mode data from a write buffer is written and additional dummy pages written to reduce the total number of pages that must be written to below a complete block size with the dummy pages providing protection from data corruption.