Multi-Dimensional Flash RAID Data Protection
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Solution Overview
Problem
As storage density in non-volatile memory devices increases, data stored in these devices becomes more prone to errors such as retention errors, page or block loss, and chip failure, leading to potential data loss and unreliability.
Innovation Solution
A persistent memory device is designed with multiple banks of nonvolatile memory cells, each with distinct dies, logically organized into quadrants with even and odd blocks and pages, using row and diagonal check words encoded with mathematical operations to ensure data protection and error correction, allowing for recovery of data even in case of page, block, or die failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage density in non-volatile memory devices is increased, then storage capacity is improved, but data reliability deteriorates due to increased susceptibility to retention errors, page or block loss, and chip failure
Solution Approach 1:
The memory device is divided into multiple banks, with each bank containing distinct dies. Each die is further segmented into memory arrays with blocks organized into even and odd groups, and pages similarly organized. This hierarchical segmentation isolates errors to specific segments, preventing catastrophic failure of the entire storage system and enabling targeted error correction while maintaining high storage capacity.
Solution Approach 2:
The patent introduces a two-dimensional RAID protection scheme by organizing data elements into rows and columns across multiple banks, blocks, and pages. Row check words protect horizontal rows of data elements, while diagonal check words protect diagonal sets. This multi-dimensional organization creates redundant protection paths, allowing data recovery even when storage density increases and error rates rise.
2Reliability
If multi-dimensional RAID protection with row and diagonal check words is implemented, then data reliability is improved, but device complexity increases due to additional memory structures and error correction mechanisms
Solution Approach 1:
The complex error correction system is segmented into manageable components: row check words for horizontal protection, diagonal check words for diagonal protection, and organized memory structures with even and odd blocks and pages. This segmentation makes the complex RAID protection scheme implementable and maintainable while achieving high data reliability.
Solution Approach 2:
The memory device structure serves multiple functions simultaneously: it provides data storage, error detection, error correction, and data recovery capabilities. The same organized structure of banks, blocks, and pages that enables high storage density also facilitates the multi-dimensional RAID protection scheme, making the system versatile and efficient rather than adding redundant complexity.
Data Source
AI summary
A method for recovering corrupted data stored in persistent memory provides protection against, at least, loss of a single block, loss of a single page, as well as a high number of random retention errors. In some implementations, each data element in a quadrant of the persistent memory is protected by a row check word and a diagonal check word. Each row check word includes a value resulting from a mathematical operation performed on a respective row set comprising a set of data elements and each diagonal check word in the quadrant includes a value resulting from a mathematical operation performed on a respective diagonal set comprising a set of data elements distributed over the banks, blocks and pages in the quadrant so that failure of any one page, block or die in the quadrant does not result in the loss of any data in the quadrant.