Scenario:
Some ESXi hosts can see and access virtual machine files in a set of NFS datastores. From another subset of hosts, these same datstores appear in vSphere client and you can select "Browse Datastore", but the VM files do not appear. The problem subset of hosts all began having this problem at the same time.
Within ESXi, at the command line you can cd to the directory that pertains to the datastore, but an ls command will not list the contents.
The problem is only on SOME datastores on the storage system, and only on SOME ESXi servers in the environment.
What could cause this?