VMware ESX mount nfs datastores

Add NFS datastores with error message:
Call "HostDatastoreSystem.CreateNasDatastore" for object "ha-datastoresystem" on ESX failed.

Solution:
http://blog.jeffcosta.com/2011/01/10/hostdatastoresystem-createnasdatastore-for-object-ha-datastoresystem-error-when-setting-up-vmware-nfs-data-store/