I/O Fencing via Coordination Storage Identifiers
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Solution Overview
Problem
In clustered environments, especially within appliances, performing input/output fencing operations without dedicated arbitrators is challenging due to the secure and unmodifiable nature of appliances, which prevents the use of external coordination points for preventing data corruption during node failures and network partitions.
Innovation Solution
The method involves storing a coordination storage identifier as metadata in a storage device, allowing nodes to perform I/O fencing operations by accessing configuration files and using fencing mode metadata to identify coordinators and data disks, and employing SCSI-3 key-based reservations to manage access to shared storage, enabling I/O fencing without dedicated arbitrators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external coordination points are used for fencing operations, then fencing capability is improved, but appliance security and unmodifiable nature is compromised
Solution Approach 1:
The patent introduces an intermediary mechanism by using metadata stored in existing appliance storage to enable fencing operations. Instead of external coordination points, the system uses coordination storage identifiers embedded in the appliance's own storage metadata, allowing nodes to perform fencing operations internally without compromising appliance security or requiring external devices.
Solution Approach 2:
The appliance performs fencing operations using its own internal resources - specifically, metadata stored in its existing storage devices. Each node can independently perform fencing by accessing and verifying coordination storage identifiers in the metadata, eliminating the need for external arbitrators and maintaining the appliance's self-contained security model.
2Reliability
If dedicated arbitrators are used for fencing operations, then data corruption prevention is improved, but device complexity increases
Solution Approach 1:
The patent merges the fencing functionality with the existing storage metadata structure. Coordination storage identifiers are embedded within the metadata that already exists in appliance storage devices, combining the fencing mechanism with the storage management infrastructure rather than adding separate dedicated arbitrators.
Solution Approach 2:
The existing storage metadata is given multiple functions - it continues to serve storage management purposes while simultaneously providing the coordination information needed for fencing operations. The same metadata structure supports both storage operations and fencing decisions, eliminating the need for separate fencing infrastructure.
3Adaptability or versatility
If metadata with coordination identifiers is stored in existing storage, then fencing without arbitrators is enabled, but storage space is consumed
Solution Approach 1:
The coordination storage identifiers are merged into the existing metadata structure of appliance storage devices. Rather than creating separate storage structures for fencing information, the system embeds these identifiers within the metadata that already exists for storage management, utilizing unused or existing metadata fields.
Data Source
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AI summary
Disclosed herein are methods, systems, and processes to perform input/output (I/O) fencing without dedicated arbitrators. A coordination storage identifier is stored in a storage device as metadata. The coordination storage identifier is associated with a node of a cluster coupled to the storage device, and an I/O fencing operation is performed using the coordination storage identifier.