SAS Controller Annular Topology for Redundant Expansion Card Routing
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Solution Overview
Problem
The Serial Attached Small Computer System Interface (SAS) system faces instability and reliability issues due to its tree-like networking structure, which can lead to communication failures and increased fault probabilities when faults occur in the routing path between expansion cards.
Innovation Solution
The SAS system is redesigned with an annular topology structure where two expansion cards connected from different ports of the same expansion card provide direct connections to the SAS controller, ensuring at least two communication channels, and the SAS controller initiates an expansion card traversal to establish routing tables based on the topology structure, skipping circularly connected expansion cards to prevent loop formation and enhance reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a tree-like networking structure is used in the SAS system, then the system can be simply configured and manufactured, but the reliability and stability decrease when faults occur in the routing path
Solution Approach 1:
The patent transforms the traditional tree-like topology into an annular (circular) topology where expansion cards are connected in a closed loop rather than a hierarchical tree structure. This curvature transformation provides redundant communication paths around the loop, allowing data to travel in opposite directions if one path fails, thereby resolving the contradiction between simple configuration and high reliability
2Adaptability or versatility
If the depth of cascading between expansion cards is increased to expand the system, then the expansion capability is improved, but the fault probability and loss increase
Solution Approach 1:
The patent changes the topological dimension from a deep hierarchical tree structure to a distributed annular structure where expansion cards connect to multiple neighbors in a loop. This dimensional transformation allows the system to expand capacity while maintaining shorter communication paths and redundant routes, preventing the exponential increase in fault probability that occurs with increased cascading depth
3Reliability
If an annular topology structure is implemented, then the reliability and stability are improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple communication paths into a unified annular topology where expansion cards simultaneously serve as both endpoints and intermediate nodes in the loop. This consolidation creates redundant paths without proportionally increasing device complexity, as each expansion card's additional connections are utilized for both expansion and fault tolerance purposes
Data Source
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AI summary
Embodiments of the present invention disclose an SAS system, an SAS system traversal method, and an apparatus. The SAS system includes: an SAS controller, a first expansion card, a second expansion card, and a third expansion card, where the first expansion card includes a first port and a second port; the second expansion card and the third expansion card establish a communication connection to the SAS controller by using the first expansion card; the first expansion card establishes a communication connection to the second expansion card through the first port; the first expansion card establishes a communication connection to the third expansion card through the second port; and the second expansion card is connected to the third expansion card. The embodiments of the present invention propose an SAS system, which can improve running reliability of an expansion card in the SAS system.