Storage Controller Path Selection via Delay Prediction
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Solution Overview
Problem
In storage systems with multipath connections, the existing referral specification methods lead to IO delays due to cross-access between controllers, where data transfer between different controller-managed blocks results in prolonged response times and performance deterioration, especially when the time required for a REPORT REFERRALS command exceeds the delay caused by cross-access.
Innovation Solution
An information processing apparatus that predicts and compares the delay time due to inter-controller communication (cross-access delay time) with the response time for a REPORT REFERRALS command, deciding whether to issue the inquiry based on this comparison, thereby suppressing unnecessary inquiries when the response time equals or exceeds the expected delay time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a REPORT REFERRALS command is issued to the storage device to obtain recommended path information for each block group, then path selection accuracy is improved, but IO processing time increases due to the command response delay
Solution Approach 1:
The system performs preliminary classification of block groups into first block groups (requiring referral information) and second block groups (not requiring referral information) before issuing IO commands. This preliminary action allows the system to avoid issuing REPORT REFERRALS commands for second block groups, thereby reducing IO processing time while maintaining path selection accuracy for block groups that truly need it.
Solution Approach 2:
The patent applies different path selection strategies to different block groups based on their characteristics. First block groups undergo referral-based path selection for high accuracy, while second block groups use alternative path selection methods. This local differentiation optimizes overall system performance by applying the costly referral mechanism only where necessary.
2Productivity
If referral specification is used to suppress cross-access delay, then data access performance is improved, but system complexity increases due to additional command processing
Solution Approach 1:
The system segments block groups into first block groups (managed by one controller) and second block groups (managed by another controller) based on their access patterns and controller ownership. This segmentation allows the system to apply referral specification selectively only to first block groups, reducing unnecessary command processing and system complexity while maintaining data access performance where it matters most.
Solution Approach 2:
The system changes the parameter of block group classification from a uniform approach to a differentiated approach based on controller management. By identifying which controller manages which block group and adjusting the referral specification application accordingly, the system optimizes data access performance without unnecessarily increasing complexity.
Data Source
AI summary
An information processing apparatus is connected through a plurality of paths to a plurality of controllers included in a storage device and includes a processor. The processor is configured to issue, to the storage device, an inquiry about a recommended path through which a data access command is to be issued to the storage device. The processor is configured to compare a delay predictive time with a response predictive time in regard to the data access command. The delay predictive time is a predictive value of a delay time due to a data communication using an inter-controller communication between the plurality of controllers. The response predictive time is a predictive value of a response time when the inquiry is issued to the storage device. The processor is configured to suppress the issuance of the inquiry when the response predictive time is equal to or longer than the delay predictive time.