Flash Memory RAID Vertical Error Correction
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Solution Overview
Problem
Flash memory cells can malfunction due to particles or mask defects during manufacturing, leading to failures in accessing storage units, which can result in data loss and require methods to protect stored data.
Innovation Solution
A method and apparatus that utilize a sector-decoding unit and a RAID-decoding unit to activate a vertical correction procedure when horizontal error correction fails, allowing the RAID-decoding unit to recover data by reading content from other sectors within a RAID group, enabling data recovery through storage-unit access interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If horizontal ECC error correction is used for flash memory sectors, then data integrity is improved, but data recovery capability is insufficient when errors exceed correction thresholds
Solution Approach 1:
The patent transitions from one-dimensional horizontal ECC correction within a single sector to two-dimensional RAID group-level correction. By organizing sectors into RAID groups with distributed parity information across multiple sectors, the system enables cross-sector data recovery when horizontal ECC fails, effectively adding a spatial dimension to error correction capability.
Solution Approach 2:
The patent segments the storage system into RAID groups containing multiple sectors, where each sector contains portions of data and parity information. This segmentation allows the system to isolate and recover data from failed sectors by accessing other sectors within the same RAID group, preventing complete data loss even when individual sectors malfunction.
2Productivity
If manufacturing processes are simplified, then production efficiency is improved, but data reliability deteriorates due to particles and mask defects
Solution Approach 1:
The patent implements beforehand cushioning by pre-distributing parity information across RAID groups during the manufacturing process. This proactive approach creates a safety buffer that compensates for potential manufacturing defects such as particles and mask defects, allowing data recovery without requiring complex re-manufacturing processes.
3Loss of information
If vertical correction procedure is activated for data recovery, then data recovery capability is improved, but processing time increases due to reading multiple sectors
Solution Approach 1:
The patent applies preliminary action by pre-organizing data and parity information across RAID groups during the writing phase. This preliminary arrangement enables the vertical correction procedure to efficiently locate and retrieve necessary data from specific sectors without exhaustive searching, reducing the time penalty associated with cross-sector data recovery.
Data Source
AI summary
An embodiment of a method for accessing a storage unit of a flash memory, performed by a processing unit, includes at least the following steps. After a notification indicating that errors presented in a message of a sector within a RAID (Redundant Array of Independent Disk) group cannot be fixed by an error correction algorithm with a horizontal ECC (Error Correction Code) of the sector is received, addresses of the other sectors within the RAID group are determined. Information is provided to a sector-decoding unit and a RAID-decoding unit, which indicates that a vertical correction procedure has been activated. Storage-unit access interfaces are directed to read content from the determined addresses of the storage unit, thereby enabling the RAID-decoding unit to recover the message of the sector by using the read content.