The NSX Controller cluster must have three members for production deployments to avoid any outage to the NSX control plane. Each controller should be placed on a unique hypervisor host, three physical hypervisor hosts in total, to avoid a single physical hypervisor host failure impacting the NSX control plane. For lab and proof-of-concept deployments where there are no production workloads, it is acceptable to run a single controller to save resources.
An NSX Controller cluster must have majority to function normally. If two out of three members are online, the cluster still has majority. You should restore the three-member cluster by bringing up the offline NSX Controller. If you cannot bring it up, you can replace it. See Replace a Member of the NSX Controller Cluster.
If only one of the three members is online, the cluster does not have majority, and will not function normally. If you cannot bring up either of the offline members, you can replace the failed NSX Controllers or redeploy the NSX Controller cluster. See Redeploy the NSX Controller Cluster.
- Verify that the appliances have network connectivity, and resolve if not.
- Reboot the appliances.
What to do next
Get the NSX Controller cluster status. See Get the NSX Controller Cluster Status.