RAID Subsystem Split-Brain Avoidance via Ordinal Claims
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Solution Overview
Problem
In storage systems, the 'split-brain' scenario occurs when mirrored data sets diverge due to system outages or maintenance, leading to inconsistent data views upon reconnection, which can result in data loss and integrity issues during disaster recovery.
Innovation Solution
The RAID subsystem implements procedures for disaster takeover and storage healing, assigning new names to volumes, retaining prior state information, and using ordinal claims to resolve naming conflicts, ensuring consistent data integrity and preventing recombination of divergent data sets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mirrored data sets are maintained for disaster recovery, then data reliability is improved, but data consistency deteriorates when systems diverge during outages
Solution Approach 1:
The system performs preliminary actions by maintaining state information and assigning ordinal claims before disasters occur. When a disaster happens, these pre-established mechanisms automatically prevent split-brain scenarios without requiring real-time coordination between diverged systems.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of ordinal claims and state information that mediates between diverged mirrored data sets. This intermediary allows the system to automatically resolve conflicts and determine which data set should be restored, preventing data consistency issues.
2Adaptability or versatility
If volume names are reused after disk removal, then storage flexibility is improved, but naming conflicts arise when disks are reinserted
Solution Approach 1:
The system implements feedback by continuously tracking the state and naming history of volumes. When a disk is reinserted, the system checks for naming conflicts against stored state information and automatically resolves conflicts by assigning new names, preventing data loss and ensuring system stability.
3Productivity
If automatic failover is implemented, then system availability is improved, but data integrity risks increase during disaster recovery
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of ordinal claims and state information that mediates between diverged mirrored data sets. This intermediary allows the system to automatically resolve conflicts and determine which data set should be restored, preventing data consistency issues.
Solution Approach 2:
The system performs self-service by automatically detecting naming conflicts and resolving them without human intervention. The conflict resolution mechanism autonomously assigns new volume names and updates state information, ensuring data integrity while maintaining high system availability.
Data Source
AI summary
A data storage system has two computers. Each computer is assigned to a set of data. Two copies of each set of data are maintained. A first copy is stored on a first set of disks and a second copy is stored on a second set of disks. Each time that a data is written by a computer, a label is written to each set of disks, the label having fields for a status of each computer, a first ordinal which is increased each time that a new data is written, and a time stamp giving a time at which the last write was performed. After failure of a computer, a processor determines, in response to reading the labels of the first set of disks and the second set of disks, the most up to date copy of the data assigned to the failed computer.