This section provides information on identifying cause for NSX Controller failure and troubleshooting controllers. Understanding the Controller Cluster Architecture The NSX Controller cluster represents a scale-out distributed system, where each controller node is assigned a set of roles that define the type of tasks the node can implement. For resiliency and performance, deployments of controller VM should be in three distinct hosts. NSX Controller Deployment IssuesNSX Controllers are deployed by NSX Manager in OVA format. Having a controller cluster provides high availability. Deploying controllers requires that NSX Manager, vCenter Server, and ESXi hosts have DNS and NTP configured. A static IP pool must be used to assign IP addresses to each controller. Troubleshooting Disk LatencyYou can view disk latency alerts from the Management tab. NSX Controllers must operate on disks with low latency. NSX Controller Cluster FailuresWhen one of the NSX Controller nodes fails, you still have two controllers that are working. The cluster majority is maintained, and the control plane continues to function. NSX Controller Is DisconnectedIf the NSX Controller VM was powered off from vCenter Server or a controller VM was deleted from the vCenter Server, the Status column of the Installation and Upgrade > Management page displays Out of sync status. Control Plane Agent (netcpa) IssuesOn NSX Data Center for vSphere, control plane (netcpa) works as a local agent daemon, communicating with NSX Manager and with the controller cluster. Communication Channel Health feature is a health check which periodically reports the central control plane to local control plane status to NSX Manager and is displayed at the NSX Manager UI. This report also serves as a heartbeat to detect the operational status of the NSX Manager to ESXi host netcpa channel. It provides error details during communication faults, generates an event when a channel goes into a wrong status, and also generates heartbeat messages from NSX Manager to hosts.