You run PostgreSQL or any other DB server with its DB data dir on the NFS mount.
Oracle supports this- and they even wrote a user-space NFS client to "get the highest level of performance" (because they thought the kernel NFS implementation sucked).
The important bit is to ensure the NFS client and server implementation handle whatever POSIX features are required by the DB server.
Why would you want to? You can't share across two instances at the same time anyway, it's going to be slower/more edge case-y, and the cost with Amazon is higher?
Oracle supports this- and they even wrote a user-space NFS client to "get the highest level of performance" (because they thought the kernel NFS implementation sucked).
The important bit is to ensure the NFS client and server implementation handle whatever POSIX features are required by the DB server.