CPLD-Based Main BMC Arbitration in Multi-Host Servers
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Solution Overview
Problem
In multi-host server systems, when the main baseboard management controller (BMC) crashes or stops, the assembly units such as power supplies and fans become uncontrolled, leading to safety and stability issues.
Innovation Solution
A method is introduced where each BMC periodically requests control authority from a connected complex programmable logic device (CPLD), and the CPLDs communicate through interconnected interfaces to dynamically determine a main BMC. If the main BMC fails, another BMC can be identified as the main controller based on interface states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static ID-based method is used to determine the main BMC, then the control authority is clearly assigned, but the system becomes vulnerable to failures when the main BMC crashes
Solution Approach 1:
The patent implements a dynamic main BMC selection mechanism where the main BMC is not statically assigned but dynamically determined through periodic heartbeat signals and arbitration protocols. The CPLD monitors BMC status and can transfer control authority to backup BMCs when the current main BMC fails, making the system adaptive to runtime conditions rather than relying on fixed ID-based assignment.
Solution Approach 2:
The patent introduces a CPLD (Complex Programmable Logic Device) as an intermediary component that mediates between multiple BMCs and the shared assembly units. The CPLD maintains the arbitration state, monitors heartbeat signals from BMCs, and controls the assembly units based on the current main BMC status, providing a centralized coordination layer that enhances reliability without requiring complex peer-to-peer communication between BMCs.
2Reliability
If the main BMC crashes, then control is lost over assembly units, but implementing backup mechanisms increases system complexity
Solution Approach 1:
The patent implements preliminary action by pre-configuring backup BMCs and establishing arbitration protocols before any failure occurs. The CPLD is pre-programmed with the arbitration logic and maintains readiness to transfer control authority. Backup BMCs are pre-identified and can immediately assume the main BMC role when needed, eliminating the need for complex runtime decision-making during failure scenarios.
Solution Approach 2:
The patent implements a feedback mechanism through periodic heartbeat signals sent from BMCs to the CPLD. The CPLD continuously monitors these heartbeats and can detect when the main BMC fails. Based on this feedback, the CPLD can automatically transfer control authority to a backup BMC, creating a closed-loop control system that maintains reliability through continuous status monitoring and automatic response.
Data Source
AI summary
Disclosed in the present application is a multi-host system and a method for determining a main controller. The multi-host system includes a first motherboard and a second motherboard, the first motherboard includes a first baseboard management controller (BMC) and a first complex programmable logic device (CPLD), the second motherboard includes a second BMC and a second CPLD. When the first CPLD receives the control request signal from the first BMC and a first signal from the second CPLD, the first BMC is determined to be a main controller of the multi-host system, and the first CPLD outputs a second signal to the second CPLD. The present application can improve the stability and security of the multi-host system.