I2C Switch SEP Failover for SAS Enclosure Redundancy
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Solution Overview
Problem
The existing Serial Attached SCSI (SAS) storage enclosures lack redundancy in their management subsystem, leading to degraded performance when a storage enclosure processor fails, as SAS architecture prohibits inter-domain connections between controllers, preventing the use of a secondary processor as a backup.
Innovation Solution
A dual controller storage enclosure design with switching circuitry that connects either storage controller to a secondary storage enclosure processor (SEP) using a non-storage protocol interconnection, allowing for seamless failover and maintaining management capability by monitoring the primary SEP's functional status via heartbeat signals and controlling I2C switches to reconfigure connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual controller storage enclosure design is implemented, then management capability and redundancy are improved, but device complexity increases due to additional switching circuitry and interconnections
Solution Approach 1:
An I2C switch is introduced as an intermediary device to manage connections between controllers and SEP processors. The I2C switch acts as a mediator that routes communication signals between the first controller, second controller, first SEP, and second SEP without requiring direct complex interconnections between all components, thereby reducing overall system complexity while maintaining redundancy capability
Solution Approach 2:
The I2C switch is designed to serve multiple functions: it can connect the first controller to the first SEP, connect the first controller to the second SEP (for failover), connect the second controller to the second SEP, and dynamically reconfigure these connections based on operational needs. This multi-functionality reduces the need for separate dedicated connection paths for each scenario
2Adaptability or versatility
If a non-storage protocol interconnection is used for SEP connectivity, then adaptability and failover capability are improved, but device complexity increases due to additional protocol support requirements
Solution Approach 1:
The I2C protocol is utilized as a universal communication interface that can carry both storage-related management traffic and failover-related control signals. This single protocol supports multiple functions including normal SEP operation, failover detection, and connection reconfiguration, thereby improving adaptability without proportionally increasing protocol support complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures continuous management capability and performance by enabling the secondary SEP to take over in case of a primary SEP failure, maintaining operational integrity and domain isolation in a point-to-point storage environment.
Implementation Method 1
A second I2C switch is operably connected to the first controller and is configured to route a control signal from the first controller to the first I2C switch to control the first I2C switch to connect the first controller to the second SEP
Implementation Method 2
monitoring the primary SEP's functional status via heartbeat signals
Implementation Method 3
controlling I2C switches to reconfigure connections
Data Source
AI summary
An information handling system includes a storage enclosure operable to communicate with a storage initiator. The storage enclosure includes a first controller corresponding to a first storage domain for enabling access between the storage initiator and a plurality of storage targets using a storage protocol. A second controller of the system, corresponding to a second storage domain, is operable to enable access between the storage initiator and the plurality of storage targets. A second storage enclosure subsystem is part of the second controller and a second configurable extra-protocol interconnection between the second storage enclosure subsystem and the first controller enables the second storage enclosure subsystem to function as a storage enclosure subsystem for the first controller.