SAS Expander Hub Arbitrates Redundant Traffic

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Solution Overview

Problem

Current SAS switch systems face challenges in maintaining bandwidth when connecting four or more expanders, as the number of inter expander links required increases, leading to reduced bandwidth and performance degradation.

Innovation Solution

A SAS expander hub is introduced to route data traffic among multiple SAS expanders, eliminating the need for direct interconnections between them, thereby maintaining bandwidth and allowing for the connection of four or more expanders while utilizing all available PHYs for inter expander links.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If direct inter expander links are used to connect four or more expanders, then port redundancy and improved performance are achieved, but bandwidth between expanders decreases and device complexity increases

Engineering Contradiction:

Improveport redundancyVSAvoidbandwidth between expanders

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

A SAS expander hub is introduced as an intermediary device to connect multiple SAS expanders. Instead of direct peer-to-peer links between expanders, all communication passes through the hub, which manages and routes traffic between expanders. This maintains bandwidth efficiency while providing redundancy through the hub's centralized connection management.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

Multiple inter expander links are merged through a single hub device. Rather than having separate direct links between each expander pair, the hub consolidates these connections, allowing efficient routing of traffic between multiple expanders while maintaining adequate bandwidth on each physical link.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If direct inter expander links are used to connect four or more expanders, then port redundancy is achieved, but device complexity and wiring requirements increase

Engineering Contradiction:

Improveport redundancyVSAvoidinterconnect structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The SAS expander hub serves as a centralized intermediary that simplifies the interconnect structure. All expanders connect to the hub rather than requiring complex mesh networking between themselves, reducing wiring complexity and device configuration overhead while maintaining redundancy through the hub's multiple connection points.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If more expanders are interconnected using direct links, then system capacity increases, but bandwidth per expander pair decreases

Engineering Contradiction:

Improvesystem capacityVSAvoidbandwidth per expander pair

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The SAS expander hub provides a universal connection point that can interface with multiple expanders simultaneously. Each expander gains access to all other expanders through the hub, enabling system capacity to scale while maintaining consistent bandwidth characteristics through the hub's centralized traffic management and link aggregation capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8918557B2SAS expander and method to arbitrate traffic in a redundant expander system

Publication Date: 2014.12.23 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

A SAS expander configured to operate as a SAS expander hub receives IO requests from a plurality of connected SAS expanders. Each SAS expander determines if it is capable of servicing a received IO request and sending such IO requests to the SAS expander hub if necessary. The SAS expander hub relays the IO requests to SAS expanders connected to data storage devices capable of servicing such IO requests.