You can try adding the storage server with IP 127.0.0.1 - it's the default IP for localhost (the middleware server) and create the additional directory in /var/www for storage content.
These are the example settings from Infomir website:
IP: 127.0.0.1
Apache port: 88 (if you use the other port, change it to yours one)
Home directory: /var/www/media
Then you will have both middleware and storage in one server. You're welcome