SSD Sector State Set for FTL Table Size Reduction
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Solution Overview
Problem
Existing solid-state disk (SSD) technologies face challenges in efficiently handling sector-sized data writes without increasing the Flash Translation Layer (FTL) mapping table size or unnecessarily rejecting host commands, which affects data integrity and performance.
Innovation Solution
The SSD employs metadata with a sector state set indicating valid or invalid states for each sector within a data unit, allowing it to return actual data for valid sectors and error information for invalid sectors during read operations, and updates sector states during write operations without expanding the FTL table or rejecting commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the basic mapping unit of the FTL mapping table is changed to a sector, then data integrity can be verified for each sector, but the FTL mapping table size increases to 8 times the original size
Solution Approach 1:
The patent divides a data unit into multiple sectors and introduces a sector state set that tracks the validity state of each individual sector. This segmentation allows the system to verify data integrity at the sector level while maintaining the original FTL mapping table structure that operates at the data unit level, thus avoiding the exponential increase in mapping table size.
Solution Approach 2:
The patent adds a new dimension of granularity by introducing the sector state set as a separate layer between the FTL mapping table and the actual data sectors. This intermediate layer enables fine-grained sector-level tracking without requiring the main FTL mapping table to store information for each sector, thereby resolving the contradiction between verification granularity and table size.
2Reliability
If the host command is rejected when error map is detected, then data corruption is prevented, but read and write time increases and unnecessary operations are repeated
Solution Approach 1:
The patent performs preliminary validation by checking the sector state set before executing read or write operations. When a sector is marked as invalid in the sector state set, the system proactively identifies this condition and handles it appropriately, preventing wasted operations on corrupted data and reducing the time loss associated with retrying failed operations.
Solution Approach 2:
The sector state set provides continuous feedback about the validity state of each sector to the control logic. This feedback mechanism enables the system to make informed decisions about whether to proceed with operations, avoiding unnecessary retries and reducing overall operation time while maintaining data integrity.
Data Source
AI summary
A reading method for solid-state disk returns data and/or information depending on state information. A data unit stored in the solid-state disk comprises metadata and a plurality of sectors including at least two sectors of user data, the metadata comprising a sector state set indicating state information of each of the sectors in the data unit, and the state information comprising a valid state and an invalid state. In response to receiving a read command from a host to read at least one of the sectors in the data unit, the solid-state disk returns actual data to the host for one or more of the sectors in the valid state, and returns information indicating a read error to the host for one or more of the sectors in the invalid state, according to the sector state set stored in the metadata of the data unit.