I had a hell of a time using the NFS options on the Seagate BlackArmor NAS, mostly because of the lack of documentation from Seagate regarding the options necessary to actually use the damn thing as an NFS share. In my mount options, I kept getting the error:
"Connecting to NAS volume:
Unable to connect to NAS volume : NFS Error: Unable to Mount filesystem: The mount request was denied by the NFS server. Check that the export exists and that the client is permitted to mount it".

This is of course because I was specifying the wrong path to the NFS share (because of the lack of documentation on the correct path). Well, after a couple few guesses, I finally figured out what was wrong and was able to mount the device as a data store in ESX 3.5. Basically the share name was :/nas/.

Of course they don’t tell you this anywhere in the documentation, nor did I find any forum posts or other results on the web about it.

So, hopefully this helps someone out there.

Edit (8/11/13): Better instructions are here.

Instead of using “192.168.0.x:/nas/“, use “192.168.0.x://“. You can check these in the Storage->Volumes section of the built-in web GUI.