Topology-Aware Path Selection in Fabric Switch Networks

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Solution Overview

Problem

Selecting an optimal input-output path in storage systems is challenging, especially during failures, as existing technologies do not adequately consider switch topology, leading to potential continued path failures if the failure is due to a fabric switch.

Innovation Solution

Implementing switch topology-aware path selection logic in host devices, which obtains and utilizes connectivity information, including fabric switch identifiers, to select paths that avoid failed switches, ensuring efficient IO operations by considering the physical connectivity of fabric switches.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If path selection is performed without considering switch topology information, then the path selection process is simple and fast, but the selected path may route through failed fabric switches leading to continued path failures

Engineering Contradiction:

Improvepath selection reliabilityVSAvoidpath selection complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The host device obtains and stores topology information about fabric switches and their connectivity relationships before path selection is needed. This preliminary action enables the path selection logic to quickly identify and avoid failed switches by referencing pre-collected topology data, rather than gathering this information during the path selection process itself.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors fabric switch status and updates path selection decisions based on feedback about switch failures. When a fabric switch failure is detected, the path selection logic uses the stored topology information to identify alternative paths that avoid the failed switch, creating a feedback loop that improves reliability while maintaining simple decision-making rules.

Inventive Principle:

Principle #23Feedback

2Reliability

If topology information is obtained and used for path selection, then failover success rate improves by avoiding failed switches, but the path selection process becomes more complex and time-consuming

Engineering Contradiction:

Improvefailover success rateVSAvoidpath selection time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Topology information including fabric switch identifiers and connectivity relationships is collected and cached in advance. During failover events, this pre-collected data allows the path selection logic to quickly determine which paths to avoid without performing complex real-time analysis, significantly reducing the time penalty associated with topology-aware path selection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates and maintains a simplified copy or representation of the fabric switch topology in the host device. This topological map includes key relationships between switches and paths, allowing rapid path selection decisions during failover without requiring access to or analysis of the complete, complex physical network topology in real-time.

Inventive Principle:

Principle #26Copying

3Adaptability or versatility

If multiple paths are available through multiple fabric switches, then path redundancy and failover capability are improved, but the difficulty of detecting and measuring the optimal path increases

Engineering Contradiction:

Improvepath redundancyVSAvoidoptimal path identification difficulty

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The path selection logic incorporates feedback about fabric switch status and connectivity from the stored topology information. When evaluating multiple available paths, the system uses this feedback to identify which paths are affected by switch failures and which remain viable, systematically narrowing down the optimal path choice among multiple redundant options.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces complex mechanical or manual path analysis methods with automated logical operations based on topological relationships. By representing the network as a graph structure with switches and paths, the system uses algorithmic path selection that automatically identifies optimal routes through multiple redundant paths without requiring manual intervention or complex real-time measurements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11561699B2Input-output path selection using switch topology information

Publication Date: 2023.01.24 EMC IP HLDG CO LLC

AI summary

Switch topology-aware path selection in an information processing system is provided. For example, an apparatus comprises a host device comprising a processor coupled to a memory. The host device is configured to communicate with a storage system over a network with a plurality of switches. The host device is further configured to obtain topology information associated with the plurality of switches in the network, and select a path from the host device to the storage system through one or more of the plurality of switches based at least in part on the obtained topology information.