As I said here, I don't think that this is possible consistently, without major modifications in Moodle. In short:
In a Master/Slave scenario, the slave side would need to be read-only. However, there's no such thing as a read-only mode of Moodle.
In a Master/Master scenario, you need to be prepared to handle replication conflicts. Again, Moodle is not prepared for that. (Neither are virtually all other RDBMS-based applications.)
You mention a scenario where users work on the master server, and only the static files are read from a mirror site. This might be possible with moderate changes to the code, still it's not possible in Moodle as-is.