I want to ask if I can use NAS to store the main database like for example Firebird or MySQL and access this database from network ? if so how to install the database server software ?
Sure! What's your nas model?
For example in my Synology i can enable web server and install mysql + phpmyadmin just in few clicks. I just need to access in the admin panel and using the PacketManager start installing the software.
I'm sure it's possible to do the same with Qnap.