Intelligent Storage Allocation for Flash Reliability
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Solution Overview
Problem
Flash memory devices face issues with unfilled word lines and failure mechanisms, such as stuck word lines, which reduce read reliability and require a solution for effective data writing and error correction in mixed-device implementations.
Innovation Solution
A geometry-aware method of writing parity is implemented, where data and parity bits are determined using error correction coding, and parity pages are specifically targeted to fill unfilled word lines and cells, using a two-dimensional parity process that involves horizontal and vertical writing to improve data reliability and survivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is written to flash memory devices following manufacturer requirements for filling word lines and cells, then read reliability is improved, but device complexity increases due to heterogeneous implementation requirements across different flash types
Solution Approach 1:
The patent segments the storage system into multiple storage devices with different performance characteristics, organizing them into performance groups. Data is distributed across these segmented devices according to their capabilities, allowing each device to operate within its optimal parameters while collectively achieving high reliability without requiring complex heterogeneous management
Solution Approach 2:
The patent changes the parameter of data placement strategy by using performance-based grouping rather than device-type-specific filling rules. This abstracts away the complex manufacturer-specific requirements into a unified parameter-based approach, maintaining reliability through performance matching while reducing implementation complexity
2Reliability
If error correction coding is applied to RAID stripes, then data reliability is improved, but writing overhead increases due to additional parity calculation and writing operations
Solution Approach 1:
The patent performs preliminary actions by pre-calculating and pre-positioning parity information during the data writing process. By preparing error correction data in advance and integrating it into the write operation, the system minimizes additional overhead while ensuring data reliability through proactive error protection rather than reactive correction
3Reliability
If parity pages are written to fill unfilled word lines and cells, then read reliability is improved, but the complexity of the writing process increases due to targeted parity placement requirements
Solution Approach 1:
The patent introduces a new dimension to parity writing by implementing two-dimensional parity protection that operates both across RAID stripes and within individual flash devices. This dimensional approach allows parity to be placed in unfilled word lines and cells systematically, transforming a complex placement problem into a structured grid-based solution that improves reliability while managing complexity through geometric organization
Data Source
AI summary
Corresponding performance characteristics for storage devices are identified. A calculation is performed using the corresponding performance characteristics for the storage devices. A set of storage devices is allocated for storage of shards of a redundant array of independent drives (RAID) stripe based on results of the calculation.