You can mount a datastore you previously unmounted. You can also mount a datastore on additional hosts, so that it becomes a shared datastore.
A VMFS datastore that has been unmounted from all hosts remains in inventory, but is marked as inaccessible. You can use this task to mount the VMFS datastore to a specified host or multiple hosts.
If you have unmounted an NFS or a Virtual Volumes datastore from all hosts, the datastore disappears from the inventory. To mount the NFS or Virtual Volumes datastore that has been removed from the inventory, use the New Datastore wizard.
A datastore of any type that is unmounted from some hosts while being mounted on others, is shown as active in the inventory.