Redundant Memory Controller Failover for Bank Access
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Solution Overview
Problem
Conventional processor-to-memory architectures lack an effective mechanism for redundant memory access, leading to data loss in case of processor failure, as each processor relies on a single access point to dedicated or shared memory.
Innovation Solution
Implementing a method and apparatus that uses multiple memory controllers connected to the same bank of memory, where a redundant controller is activated to take over memory access upon failure, supporting redundant data/address/control interconnect paths and avoiding coherency issues by not using the memory as primary storage during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single memory controller is used for each processor, then the architecture is simple and easy to implement, but the system loses data and cannot operate when the processor or memory controller fails
Solution Approach 1:
The system divides memory controller functionality into primary and redundant segments. Each processor has a dedicated primary memory controller for normal operation, while a separate redundant memory controller stands by to take over upon failure. This segmentation allows the system to maintain simplicity during normal operation while achieving high reliability through failover capability.
Solution Approach 2:
The patent implements beforehand cushioning by pre-configuring redundant memory controllers that remain inactive during normal operation but are ready to activate immediately upon failure. This prior preparation ensures that when a primary controller fails, the system can seamlessly switch to the redundant controller without data loss or operational interruption, thus cushioning against potential failures.
2Reliability
If redundant memory controllers are implemented, then failover capability is achieved, but system complexity and resource requirements increase
Solution Approach 1:
The system performs preliminary action by pre-establishing the redundant memory controller infrastructure and configuring failover protocols before any failure occurs. The redundant controllers are initialized and ready with predetermined failover procedures, eliminating the need for complex real-time decision-making during failures. This preliminary setup simplifies the overall system architecture while ensuring reliable failover capability.
3Loss of time
If the redundant controller uses the same memory bank, then failover is faster, but coherency issues arise during normal operation
Solution Approach 1:
The patent applies taking out by extracting the redundant controller from active participation in normal memory operations. The redundant controller is disconnected from the memory bank during normal operation, eliminating coherency management requirements. When failover is needed, the redundant controller is quickly connected to the same memory bank, enabling fast failover without having managed coherency protocols during normal operation.
Data Source
AI summary
A method and apparatus implement redundant memory access using multiple controllers on the same bank of memory. A first memory controller uses the memory as its primary address space, for storage and fetches. A second redundant controller is also connected to the same memory. System control logic is used to notify the redundant controller of the need to take over the memory interface. The redundant controller initializes if required and takes control of the memory. The memory only needs to be initialized if the system has to be brought down and restarted in the redundant mode. This invention allows the system to continue to stay up and continue running during a memory controller or link failure.