Hot Spare RAID Storage Rebuilding via XOR Parity
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Solution Overview
Problem
RAID systems face data loss when two or more drives fail in a group of mirrored drives, as existing methods do not effectively rebuild data in a hot spare storage device to maintain redundancy and recover missing data.
Innovation Solution
A method and system that utilize a hot spare storage device to rebuild data by performing XOR operations with mirrored storage devices, generating parity data to reconstruct missing data, and overwriting existing data to store rebuilt information, ensuring redundancy across failed spans.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hot spare storage device is used to rebuild data from a single failed drive, then data redundancy is maintained, but the system cannot handle multiple simultaneous drive failures
Solution Approach 1:
The patent segments the data rebuilding process into multiple sequential phases, where each phase handles one drive failure at a time. When multiple drives fail, the system rebuilds to the hot spare in phases, overwriting the hot spare's original data with parity information from subsequent failed drives, thereby maintaining reliability across multiple failures.
Solution Approach 2:
The patent changes the functional parameter of the hot spare storage device from storing original data copies to storing parity data through XOR operations. This parameter change allows the hot spare to adaptively serve multiple failed drives by transforming its data content through mathematical operations with data from newly failed drives.
2Reliability
If the hot spare storage device stores original data copies, then single drive failure recovery is enabled, but multiple drive failures result in data loss
Solution Approach 1:
The patent converts the harmful situation of multiple drive failures into a beneficial process by using XOR parity operations. When additional drives fail after the hot spare is occupied, the system performs XOR operations between the hot spare's current data and data from the new failed drive, generating new parity data that preserves information from all failed drives.
Solution Approach 2:
The hot spare storage device acts as an intermediary that mediates between multiple failed drives. It temporarily holds and transforms data from failed drives through XOR operations, serving as a computational intermediary that reconstructs and preserves data from multiple failure sources before final restoration.
3Manufacturing precision
If existing data in the hot spare is preserved, then original data integrity is maintained, but the hot spare cannot be reused for subsequent drive failures
Solution Approach 1:
The patent implements a discard and recover mechanism where the hot spare's original data is temporarily discarded when a drive fails, allowing the hot spare to be repurposed for rebuilding. After the rebuild process completes and parity data is established, the system can recover and restore original data from remaining functional drives, thereby maintaining both data integrity and hot spare reusability across multiple failure cycles.
Data Source
AI summary
A method provides rebuilding data in a hot spare storage device when multiple storage devices fail in a storage system. The method includes a storage controller determining if a first storage device storing first data has failed within a first group of storage devices. In response to the first storage device failing, the first data is rebuilt in the hot spare storage device from a copy of the first data stored in a first mirrored storage device of the first group of storage devices. In response to a second storage device failing, third data is generated by performing a first exclusive or (XOR) operation with the first data stored on the hot spare storage device and a copy of the second data stored in a second mirrored storage device of the second group of storage devices. The third data is rebuilt in the hot spare storage device. The method recovers original data and prevents complete failure of a virtual disk.