Storage System I/O Prioritization via Logical Path Evaluation
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Solution Overview
Problem
In storage systems, the concentration of virtual servers on a single physical host leads to inefficiencies due to mixed response delays among logical volumes, causing processing delays or stoppages in virtual servers and their applications, especially when I/O operations are transferred between storage devices over a network.
Innovation Solution
The system connects multiple hosts to a processor-managed storage system where logical volumes are grouped into High Availability (HA) pairs across different storage devices, allowing I/O operations to be prioritized based on path evaluation, ensuring consistent and uninterrupted data access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If I/O operations are transferred between storage devices over a network to achieve high availability, then the availability of logical volumes is improved, but the response delay increases and processing speed deteriorates
Solution Approach 1:
The system segments I/O operations into two categories: local I/O operations that are processed directly by the storage device without network transfer, and remote I/O operations that require network transfer between storage devices. This segmentation allows the system to maintain high availability through network-based redundancy while preserving fast local response times for routine operations.
Solution Approach 2:
The patent introduces an intermediary mechanism that evaluates the state of logical paths and determines whether I/O operations should be processed locally or transferred remotely. This intermediary layer (the evaluation unit) mediates between the conflicting requirements of high availability and fast response by routing operations appropriately based on current system conditions.
2Reliability
If I/O operations are transferred between storage devices over a network to ensure high availability, then the reliability is improved, but the processing delay increases causing virtual server stoppages
Solution Approach 1:
The system performs preliminary evaluation of logical path states before I/O operations are executed. By evaluating the state of logical paths in advance (using evaluation values that reflect current system conditions), the system can proactively route I/O operations through optimal paths, preventing delays and stoppages before they occur.
Solution Approach 2:
The patent implements a feedback mechanism where the state of logical paths is continuously evaluated and used to adjust I/O routing decisions. The evaluation unit monitors system conditions and provides feedback that influences subsequent I/O operation routing, allowing the system to adapt to changing conditions and minimize processing delays while maintaining availability.
3Adaptability or versatility
If multiple SLUs with various response delays are accessed via a single logical path, then the functionality is maintained, but the processing delay or stoppage occurs
Solution Approach 1:
The system dynamically adjusts I/O routing based on the evaluated state of logical paths rather than using a static routing configuration. The evaluation values reflect current system conditions, allowing the routing behavior to adapt dynamically to changing response delays and system states, thereby maintaining functionality while optimizing throughput.
Solution Approach 2:
The patent changes the parameter used for I/O routing from a fixed logical path identifier to a dynamic evaluation value that reflects current system conditions. By using evaluation values that incorporate real-time state information, the system can select optimal I/O targets that minimize delay while maintaining the required functionality for accessing multiple SLUs.
Data Source
AI summary
An information system connected to hosts and an information processing system manages a second ALU connected to the hosts via a second logical path, and second SLUs for receiving I/O requests from the hosts via the second logical path. A processor manages a first ALU connected to the hosts via a first logical path and first SLUs that receive I/O requests from the hosts via the first logical path, and builds up a first group including the first SLUs. A first SLU and a second SLU compose an HA pair, and the HA pair is provided to the hosts as one volume. The processor evaluates the state of the first logical path based on the pair state of the first SLU that composes the HA pair included in the first group so priorities with which the hosts issue I/Os to the first logical path can be determined.