When you remove a host from a DRS cluster, you affect resource pool hierarchies, virtual machines, and you might create invalid clusters. Consider the affected objects before you remove the host.
Resource Pool Hierarchies – When you remove a host from a cluster, the host retains only the root resource pool, even if you used a DRS cluster and decided to graft the host resource pool when you added the host to the cluster. In that case, the hierarchy remains with the cluster. You can create a host-specific resource pool hierarchy.Note:
Ensure that you remove the host from the cluster by first placing it in maintenance mode. If you instead disconnect the host before removing it from the cluster, the host retains the resource pool that reflects the cluster hierarchy.
Virtual Machines – A host must be in maintenance mode before you can remove it from the cluster and for a host to enter maintenance mode all powered-on virtual machines must be migrated off that host. When you request that a host enter maintenance mode, you are also asked whether you want to migrate all the powered-off virtual machines on that host to other hosts in the cluster.
Invalid Clusters – When you remove a host from a cluster, the resources available for the cluster decrease. If the cluster has enough resources to satisfy the reservations of all virtual machines and resource pools in the cluster, the cluster adjusts resource allocation to reflect the reduced amount of resources. If the cluster does not have enough resources to satisfy the reservations of all resource pools, but there are enough resources to satisfy the reservations for all virtual machines, an alarm is issued and the cluster is marked yellow. DRS continues to run.