What exactly do you mean by "Administration Server is on shared storage(NAS)."? Is your domain home on the NAS?
We do have a similar setup, just we have installed everything on the primary server.
Yes. Admin Server domain is on the NAS.
I don't know how to upgrade in this case...
I'm not getting how you have installed just the Admin Server on the NAS...
Sorry to ask again, but can you get a screenshot of the NAS location for all the folders related to OBIEE installation?
Can you also share the folder structure for both NAS and node1/node2?
The structure that you have designed is a very complex one.
Usually, when we refer DOMAIN, it means each and every component under USER_PROJECTS/DOMAINS/<DOMAIN_NAME> folder (Admin Server, BI_Server, config files, scripts, etc).
In your case as you have separated the domain components, so I am not sure how you will bring all the components at one place for upgrade (I'm not sure if there is a way for part-wise upgrade).
Also, my suggestion will be to try to run the upgrade assistant post taking a complete backup of the system.
Thanks in advance for your any information.