SAS Expander Redundant Interconnect for RAID Controller Failover
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Solution Overview
Problem
In SAS RAID environments, existing systems lack a robust and redundant interconnection method between SAS RAID controllers across separate storage subsystems, making them vulnerable to failures and requiring complex routing and address mapping considerations.
Innovation Solution
A system comprising at least two SAS controllers in separate storage subsystems, each connected to expander devices that are cross-connected via redundant wide SAS physical interconnections, utilizing differential pair links for fail-over protection and minimizing routing table size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SAS RAID controllers are housed in separate storage subsystems to provide redundancy, then system reliability is improved, but interconnection complexity increases due to routing and address mapping restrictions
Solution Approach 1:
The patent introduces expander devices as intermediary components that simplify the interconnection between SAS RAID controllers in separate subsystems. The expander devices handle the complex routing and address mapping, acting as mediators that translate controller requests into appropriate physical connections, thereby reducing the complexity burden on the controllers themselves while maintaining reliable cross-subsystem connectivity
2Reliability
If redundant physical connections are implemented between expander devices, then fail-over protection is improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the redundant connection path into multiple independent physical connections between expander devices. Instead of implementing complex redundancy within a single connection, the system divides the redundancy function across separate physical links, allowing fail-over to occur at the connection level while keeping individual connection complexity manageable
3Reliability
If multiple wide SAS physical interconnections are used for cross-connecting expander devices, then interconnect reliability is improved, but routing table size increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring routing tables in expander devices during system initialization or setup phases. The routing information for multiple wide SAS physical interconnections is established in advance, allowing the expander devices to efficiently forward traffic across redundant connections without requiring dynamic routing table expansions during operation, thus maintaining manageable routing table sizes while supporting high-reliability multi-path connectivity
Data Source
AI summary
A system comprising a first expander device and a second expander device. The first expander device and the second expander device comprise a subtractive port and a table mapped port and are suitable for coupling a first serial attached SCSI controller to a second serial attached SCSI controller. The first and second expander devices are cross-coupled via a redundant physical connection.