I would separate DMZ and the production network with IPSpaces.
In my opinion the following arguments are used to separate SVMs:
- SVM-DR
- Domain Admins have rights on Active Directory joined SVMs
- If you use NFS SVMs for VMWare Datastore you need a user for a backup tool (like VSC) and you don't want to share the cifs volumes with this user (cloning, destroying and so on)
- Routing issues as mentioned
- Administrative issues: if for example the server team wants to administrate the CIFS Shares on their own and you don't want them to create shares on the NFS volumes
So it really depends on what you're using on this SVMs.