Multi-Dimensional RAID Grid Data Reconstruction

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Solution Overview

Problem

Current data replication schemes in storage systems are limited in their ability to handle errors, often becoming unable to read data after a certain number of errors occur, which can lead to data loss.

Innovation Solution

A multi-dimensional RAID scheme is implemented, using a 2D or 3D RAID structure that stores out-of-band data within each page to enable reconstruction of pages within the RAID grid, even when multiple errors occur, by selecting parity locations based on whether underlying physical storage locations are defective.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If current replication schemes are used, then data storage is simple, but the system becomes unable to read data after a limited number of errors occur

Engineering Contradiction:
Improvedata readability after errorsVSAvoidRAID structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent transitions from traditional linear RAID structures to multi-dimensional RAID grids (2D, 3D, or higher dimensions). Data is organized in d-dimensional grids where each dimension represents a fault domain, enabling recovery from multiple simultaneous errors across different dimensions while maintaining systematic complexity management.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The storage system is segmented into multiple independent fault domains along different dimensions. Each dimension represents a separate failure mode or storage component group, allowing errors to be isolated and recovered independently without affecting the entire system, thus improving reliability while managing complexity through structured segmentation.

Inventive Principle:
Principle #1Segmentation

2Reliability

If traditional RAID schemes are used, then the system structure is simple, but fault tolerance is limited to a certain number of errors

Engineering Contradiction:
Improvefault tolerance capabilityVSAvoidmulti-dimensional RAID structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements d-dimensional RAID grids where data pages are distributed across multiple dimensions, each representing an independent fault domain. This multi-dimensional arrangement enables the system to tolerate multiple simultaneous failures across different dimensions by reconstructing lost pages using parity information from other dimensions, significantly enhancing fault tolerance beyond traditional RAID.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent combines multiple RAID schemes (e.g., RAID 5, RAID 6, RAID DP) within a unified d-dimensional grid structure. Different dimensions can employ different RAID levels or error correction codes, creating a composite fault tolerance system that leverages the strengths of multiple approaches to handle various failure scenarios more effectively than any single scheme alone.

Inventive Principle:
Principle #40Composite materials

3Reliability

If more parity information is stored to handle more errors, then fault tolerance improves, but storage efficiency decreases

Engineering Contradiction:
Improveerror recovery capabilityVSAvoidstorage capacity
Core Design Contradiction:
ReliabilityVSQuantity of substance

Solution Approach 1:

The patent distributes parity information across multiple dimensions rather than concentrating it in traditional RAID stripes. Each dimension contributes a portion of the redundancy needed for recovery, allowing the system to tolerate multiple errors while maintaining better storage efficiency. The multi-dimensional arrangement enables more efficient use of parity pages compared to single-dimension approaches.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent dynamically adjusts the number of dimensions and pages per dimension based on the desired fault tolerance level and storage efficiency requirements. By changing the dimensional parameters of the RAID grid, the system can optimize the balance between error recovery capability and storage capacity, allowing flexible configuration to match specific operational needs without being locked into fixed redundancy ratios.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP2920695B1Method and system for multi-dimensional raid reconstruction and defect avoidance
Publication Date: 2022.01.26 EMC IP HLDG CO LLC
  • EP2920695B1 patent drawingFigure 1
  • EP2920695B1 patent drawingFigure 2
  • EP2920695B1 patent drawingFigure 3

AI summary

In general, embodiments of the invention relate to storing data by receiving a request to write data, in response the request, selecting a first RAID grid location in a RAID grid to write the data, determining a first physical address in persistent storage corresponding to the first RAID grid location, generating a first page comprising the data and first out-of-band (OOB), wherein the first OOB comprises a first grid geometry for the RAID grid, and a first stripe membership for the page within the RAID grid, and writing the first page to a first physical location in persistent storage corresponding to the first physical address.