Storage Controller Ownership Rebalancing for Communication Overhead
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Solution Overview
Problem
In multi-node storage systems, existing methods for load dispersion do not consider communication overhead, leading to suboptimal ownership arrangements and degraded processing performance due to communication overhead between nodes.
Innovation Solution
A storage system with multiple controllers and physical storage devices, where ownership of logical storage devices is dynamically rebalanced based on access indices to physical storage devices and hosts, using a cross penalty index calculation to optimize CPU operation rates and reduce communication overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LDEV ownerships are assigned to controllers based on static load information, then load dispersion among controllers is achieved, but communication overhead between nodes increases due to FE cross and BE cross operations
Solution Approach 1:
The patent changes the ownership assignment parameter from static load information to dynamic cross penalty index that incorporates communication overhead considerations. The cross penalty index is calculated based on the number of FE cross and BE cross operations, and ownerships are reassigned to minimize this index, thereby reducing communication overhead while maintaining load dispersion.
2Adaptability or versatility
If controllers process I/O requests for LDEVs owned by other controllers, then system flexibility is maintained, but processing performance degrades due to communication overhead
Solution Approach 1:
The patent implements a feedback mechanism where the cross penalty index is continuously calculated based on actual FE cross and BE cross operations. This feedback information is used to dynamically adjust ownership assignments, creating a closed-loop system that optimizes processing performance by minimizing communication overhead while preserving system flexibility.
Data Source
AI summary
A storage system includes controllers, physical storage devices, and logical storage devices to which storage areas are assigned from the physical storage devices. The controllers each have the physical storage device being different from that of each other and the host connected thereto being different from that of each other, and are each able to access the physical storage device and the host that are not connected thereto, through another controller. Any one of the controllers has an ownership to process an access request concerning the logical storage device. At least one controller determines that the ownership is caused to be moved among the controllers, based on an index of accesses to the physical storage device that includes the storage area to be assigned to the logical storage device and an index of accesses to the host that accesses the logical storage device.