How Do Redundant Controllers Handle Split-Brain?
If I add another OC300 in a different location on the same LAN, a failure between the two locations could cause split-brain, where each controller does not see the other and therefore both controllers assume that they are the primary controller. Once the failure has been resolved, both controllers will see that there is another primary controller on the LAN. Does the controller HA software contemplate and handle this situation? What happens?
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Hi @Dr_Marty
Thanks for posting here.Do you mean this? How to Configure Hot-Standby Backup Mode on Omada Controller
Generally, the Primary Node is responsible for network management and process running. The Secondary Node synchronizes data with the Primary Node. When the Primary node goes down, the Secondary Node will take over network and clients management. During the failover, the devices will go offline for a short time, then they will reconnect to the new Primary Node When the devices get connected again, all services will run normally. If the previous Primary Node recovers from failover, it will continue to run as a Secondary Node.
the two locations could cause split-brain
>>> Does this mean, the two controllers loose connection with each other? It doesn't matter, the primary node will continue to manage the devices.
Let me know if I have any misunderstanding.
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@Vincent-TP Thank you for getting back to me.
Suppoose that I have two racks connected to each other as a single LAN: Rack A and Rack B. I have an OC300 in each rack configured in HA with the OC300 in Rack A operating as primary and the OC300 in Rack B operating as secondary. Suppose then that the connection between the racks goes down. Now devices in each rack cannot see the devices in the other rack.
When the Primary node goes down, the Secondary Node will take over network and clients management. During the failover, the devices will go offline for a short time, then they will reconnect to the new Primary Node
Rack A controller will see Rack B devices disappear, but will continue as the primary controller. Rack B controller will see Rack A devices disappear, including the primary controller. Rack B controller will perform as described above and assume the primary role, adopting Rack B devices. At this point Rack A controller has deemed itself as primary and Rack B controller has deemed itself as primary. Neither controller can see the other rack devices.
Now suppose that the connection between the racks is restored. At this point, all devices in each rack can see all devices in both racks. Rack A controller is primary and controlling Rack A devices but also sees that Rack B controller is operating as primary and controlling Rack B devices. Rack B controller has a similar view.
Each rack now has a primary controller controlling the dervices in that rack. What happens?
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