This section provides information on identifying cause for NSX Controller failure and troubleshooting controllers. Understanding the Controller Cluster ArchitectureThe 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. View Disk Latency AlertsDisk latency alerts monitors and reports disk availability or latency issues. You can view disk latency details for each NSX Controller. The read latency and write latency calculations are inputted into a 5-second (by default) moving average, which in turn is used to trigger an alert upon breaching the latency limit. The alert is turned off after the average comes down to the low watermark. By default, the high watermark is set to 200 ms, and the low watermark is set to 100 ms. High latencies impacts the operation of the distributed clustering applications on each controller node. Controller Out Of SyncIf 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 > Management page displays Out of sync status. Troubleshooting Controller ClusterIn case of an NSX Controller failure, you may still have two controllers that are working. First try to resolve the issue without redeploying the controller cluster. NSX Controller IssuesThis topic provides information on identifying cause for NSX Controller failure and troubleshooting NSX Controller.