DRS in cluster is not working after upgrade from 7.x to 8.x, with the error: "vSphere DRS functionality was impacted due to unhealthy state vSphere Cluster Services"

Products

• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Issue started after adding the new hosts to the cluster
• DRS not working on the specific cluster in vCenter
• vCLS VMs are not being created even after disabling / enabling DRS or vCLS retreat mode.
• You see the this alarm on cluster summary page:  "vSphere DRS functionality was impacted due to unhealthy state vSphere Cluster Services caused by the unavailability of vSphere Cluster Service VMs. vSphere Cluster Service VMs are required to maintain the health of vSphere DRS"
• On the Cluster Summary page we see the below error:
  
• Disabled and re-enabled vSphere HA, still issue persists.
• No HA issues shown in the Health Summary
• Restarted all Management Agents within the cluster, that doesn't help.
• Cluster service status shows Unhealthy

Environment

VMware vCenter Server 8.0.x

Cause

Issue with the few host's DNS configuration, not all the ESXi hosts were configured with the DNS domain suffix

Resolution

The DNS domain suffix was not configured on all ESXi hosts in cluster. After applying the configuration via Host Profiles, DRS functionality was restored.