Storage Subsystem Dynamic Path Selection for Failover
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Solution Overview
Problem
In storage subsystems with multiple controllers, access performance varies depending on the selection of access paths, and there is no method to detect failures in paths between the host and storage subsystem, making it difficult to switch to an appropriate alternate path during failures.
Innovation Solution
The storage subsystem is configured with multiple nodes of interconnected control packages, where intra-node communication has a higher data transfer rate than inter-node communication, allowing for priority changes based on failure occurrence and notification to the host computer for selecting an appropriate access path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple controllers are installed to ensure high availability, then system reliability is improved, but access performance varies depending on the selection of access paths
Solution Approach 1:
The patent implements dynamic path selection by enabling the host computer to switch between different access paths based on real-time controller status. The system transitions from static path configuration to dynamic adaptation, where the host selects optimal paths considering controller failures or performance variations, thereby maintaining high availability while ensuring consistent access performance.
Solution Approach 2:
The patent changes the parameter of path selection from fixed to variable by introducing performance information about multiple access paths. The host computer uses this information to dynamically adjust which path to use, transforming the system from one where performance varies unpredictably to one where the optimal path is selected based on current conditions.
2Reliability
If traditional duplicated controller configuration is used, then failover capability is provided, but appropriate path switching during failures cannot be achieved
Solution Approach 1:
The patent introduces feedback mechanisms where the storage subsystem provides performance information about different access paths to the host computer. This feedback enables the host to make informed decisions about path selection, transforming the system from one that merely provides failover to one that intelligently selects the best available path based on real-time performance data.
Solution Approach 2:
The patent implements preliminary action by having the storage subsystem pre-calculate and provide performance information about multiple access paths before failures occur. This allows the host computer to have advance knowledge of path qualities, enabling faster and more appropriate path switching when failures occur, rather than reacting blindly to failure conditions.
3Device complexity
If path failure detection is not implemented, then system complexity is reduced, but appropriate alternate path selection during failures becomes impossible
Solution Approach 1:
The patent applies self-service by enabling the storage subsystem to automatically provide performance information about access paths to the host computer without requiring complex external detection mechanisms. The system serves its own information needs, allowing the host to make informed path selection decisions based on data provided by the storage subsystem itself, thereby achieving adaptability without proportionally increasing complexity.
Data Source
AI summary
A storage subsystem comprises one or more volumes, and multiple nodes having multiple control packages interconnected via an intra-node communication path, wherein the control packages of different nodes are interconnected via an inter-node communication path having a lower transmission path capacity than the intra-node communication path. When the host computer accesses a volume, access is enabled via any of at least two or more control packages out of the multiple control packages, and the priority for issuing access requests to the relevant volume is determined in each of the control packages. When the storage subsystem detects failure, it changes the priorities determined for the control packages according to the failure occurrence portion, and notifies the same to the host computer. The host computer determines the control package being the issue destination of the access request based on the notified priority.