Shared Application Tier File System in DMZ

We are trying to migrate from our Non Shared APPL_TOP Architecture to shared APPL_TOP architecture. We have  2 Internal & 2 External DMZ Nodes. (Linux VM's)

Attaching the Design for review:

We have the following assumptions in implementing this design & are they realistic:

1) Our Internal and External Apps Nodes are in different domains. Can we share the same disk which is shared by the internal app nodes to the external nodes.

2) We would like to mount the shared disk as RW on the Internal App Node1 and RO for the rest of the app nodes (Including 2nd Internal app Node & 2 external DMZ web nodes), is this really possible?