ReadyNAS units that have current firmware support the NFS file system needed to be accessed as a storage device by VMWare’s ESX & ESXi server.
The process is simple in the end – though there is almost no help in forums to do this.
Using VMWare Infrastructure Client, attach to the ESXi server. Under the configuration tab, there is a link in the upper right corner labeled “Add Storage…”.
The add storage wizard comes up; select Network File System and click next.
For server, type in the IP address of the ReadyNAS, such as 192.168.1.15 (or whatever your unit’s IP is)
For folder, type in / followed by sharename, such as /Data
Name the datastore and click Next, then finish. If all is good, it will be added in a couple of seconds.
That’s it! Your ReadyNAS is now a storage device for VMWare ESX (i) server.
Find out more about ReadyNAS network storage.

{ 3 comments… read them below or add one }
As a Newbie, I am always searching online for articles that can help me.
It might be worth explaining that NFS needs to be enabled as a service (it did on my readyNAS Duo) and that it needs to be enabled for the share too.
I’ve done all that and still get:
“Error during configuration of the host. NFS Error: Unable to Mount filesystem: The mount request was denied by by the NFS server. Check that the export exists and the client is permitted to mount it.”
I even added the ESXi host as a “Root privilege-enabled hosts” for the share (even though it’s read/write access anyway).
OK, NFS shares are Case Sensitive.
/Packages instead of /packages worked.