I wonder how the synchronisation between two clusters works. my two servers have the same cluster name and node name, so synchronisation wokrs fine. I have to use elasticsearch version 1.7.6 for a project, so i cannot update (just as an information if something has changed how it works). I'd like to know what happens if a project with the same name but different data is on these two servers. Or how do I know that the synchronisation is finished and in progress?