By using Storage DRS (SDRS) to group datastores in a datastore cluster, it's possible to put a datastore in maintenance mode and evacuate all the VMs to other datastores in the same datastore cluster.
Just for the vSphere Web Client, go to the Datastore inventory and select Maintenance Mode | Enter Maintenance Mode on the desired datastore:
A list of recommendations appears for datastore maintenance mode migration.
For more information, see the vSphere 6.5 Resource Management guide (https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.resmgmt.doc/GUID-D229556E-C991-41BD-A378-363CC9D2B2CC.html ...