vCLS VMs will automatically be powered on or recreated by vCLS service. These VMs are deployed prior to any workload VMs that are deployed in a green field/fresh deployment. In an upgrade scenario, these VMs are deployed before vSphere DRS is configured to run on the clusters. When all the vCLS VMs are powered-off or deleted, the vSphere Cluster status for that cluster will turn to '
Degraded (Yellow)'. vSphere DRS needs one of the vCLS VMs to be running in a vSphere cluster to be healthy. If DRS runs prior to these VMs are brought back up, then the cluster service will be '
Unhealthy (Red)', until the time vCLS VMs are brought back up.
Scenarios with a resolution where vCLS VMs deployment could fail:
- Not enough free resource in the cluster - Requires 400 MHz of CPU, 400 MB of memory and 2 GB of storage space on a cluster with more than 3 hosts. For more information on the resource requirements for these VMs, see the vCLS VM Resource Allocation section of the vSphere Resource Management Guide. vCLS reserves slots equal to the quorum size of the VMs + 1 per cluster. vCLS VMs require this much extra resources in the clusters for successful deployment.
- Deployment failures in 1 node and 2 node vSAN cluster - vCLS VMs failed to deploy on a 1 or 2 node vSAN cluster with the error: Can't provision VM for ClusterAgent due to lack of suitable datastore. Since vCLS uses datastore default policy for datastore selection, if vSAN is the only available datastore within the cluster, then default policy requires 3 node vSAN cluster. The deployment of these VMs will fail in such a cluster. If a 2 Node vSAN cluster has a witness node, then deployment of vCLS VM succeeds. Workaround is to increase the size of the vSAN cluster or to change the datastore default policy.
- Orphaned VM cases - If there are orphaned vCLS VMs in the vCenter Server because of disconnected and reconnected hosts, deployment of new vCLS VMs in such a cluster after adding the host might fail. Suggested workaround is to clean-up any stale/orphaned vCLS VMs from the inventory.
Scenarios with a resolution where vCLS VMs power on may fail
- Not enough free resources in the cluster.
- Power-on of disconnected/orphaned vCLS VMs could fail - If there are orphaned vCLS VMs in vCenter because of disconnected and reconnected hosts, power-on of such orphaned VMs could fail as these are disconnected. The workaround is to manually delete these VMs so new deployment of vCLS VMs will happen automatically in proper connected hosts/datastores.
- Power-on failure due to changes to the configuration of the VMs - If user changes the configuration of vCLS VMs, power-on of such a VM could fail. User is not supposed to change any configuration of these VMs.