Mounting NFS Datastore on ESXi server is very easy, similar way you might need to remove/unmount NFS share from ESXi server for maintenance or migration purpose. To unmount it, open VMWare vSphere Web Client and select Storage tab, from the list select NFS datastore, right click on it and select Unmount datastore. This launches the wizard, In the wizard the datastore is accessible from the hosts listed in the list. The host(s) will no longer have access to the virtual machine files on this datastore once the access is removed. If the datastore is unmounted from all hosts it will disappear from the inventory. Select the hosts that should not have access to this datastore. Click the check box on hosts list, and OK to proceed.

Warning: If you have configured HA cluster while unmounting datastore make sure, Nfs Datastore might be used by vSphere HA for heartbeating. Once unmounted, check the 'Cluster-Monitor-Issues' page to see if any hosts now have an insufficient number of heartbeat datastores. 

Earlier useful posts
Mount NFS share to multiple ESXi hosts
VMWare ESXi add and create NFS datastore
Microsoft Windows 2016 Install and configure NFS server for ESXi and Linux
Unmount NFS datastores from VMware ESXi and NFS is in use

Next if unmounting NFS datastore shows the error The resource 'nfs' is in use (The "remove datastore" operation failed for the entity with the following error message), to resolve this, make sure that the following prerequisites are met:

• No virtual machines reside on the datastore.
• The datastore is not managed by Storage DRS.
• The datastore is not part of a datastore cluster.
• The datastore is not used for vSphere HA heartbeating.
• Storage I/O control is disabled for this datastore.

In my case NFS storage still had virtual machines running, which I migrated using storage vmotion to another drive and emptied nfs drive, also made sure there are no other  dependencies listed above, After that removing NFS was successful with no error.

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