Redundant Controller Routing for Storage Expansion
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Solution Overview
Problem
Conventional storage devices using Serial Attached SCSI (SAS) face challenges in accessing discs and enclosures when failures occur, leading to inaccessible data and complex wiring due to the inability to couple in a loop shape and the need for redundant routes, which complicates fault tolerance and expansion.
Innovation Solution
A storage device configuration with redundant controllers and enclosures, where two routes are established with controllers serially coupled in opposite orders to ensure continued access and simplify expansion, using route tables to manage access and handle failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant controllers and dual routes are implemented to ensure fault tolerance, then system reliability is improved, but device complexity increases due to additional wiring and configuration
Solution Approach 1:
The patent applies inversion by coupling the second additional controllers in reverse order compared to the first additional controllers. While the first route couples controllers in the order they were added to the system, the second route couples them in reverse order. This creates two independent access paths where a failure in one route does not affect the other, achieving fault tolerance without requiring complex switching devices or loop configurations. The reverse coupling order simplifies the wiring architecture while maintaining dual redundant paths.
2Ease of operation
If serial coupling in the order of adding enclosures is used, then ease of operation is improved, but reliability deteriorates when a failure occurs in one of the DEs on the access route
Solution Approach 1:
The patent adds a second dimension to the access path by creating two independent serial coupling routes. The first route maintains the simple serial coupling order for ease of expansion, while the second route provides an alternative path through reverse-order coupling. This dimensional addition allows the system to maintain both operational simplicity and fault tolerance, as data can be accessed through either route depending on which path is available.
3Reliability
If loop coupling is implemented to provide redundant paths, then reliability is improved, but device complexity increases due to complex wiring management
Solution Approach 1:
The patent segments the redundant path requirement into two separate serial coupling routes instead of implementing a single loop structure. Each route is independently configured and managed, avoiding the complexity of loop wiring while providing the same fault tolerance benefits. The segmentation of access paths into distinct serial chains simplifies wiring management compared to a unified loop structure.
Data Source
AI summary
In a storage device expandable through serially coupling two or more additional enclosures, each including a first additional controller and a second additional controller, to a controller enclosure, including a first controller and a second controller, a first route is formed by serially coupling the first controller of the controller enclosure to the first additional controllers of the additional enclosures in the order of adding the additional enclosures and a second route is formed by serially coupling the second controller of the controller enclosure to the second additional controllers of the additional enclosures in an order different from that of adding the additional enclosures.