lsyncd uses inotify. Also, it does rsync (or other backends) of the whole tree instead of single files AFAIK, but that's of course not a stopper as it would need few changes to implement.
In addition, I don't think lsyncd has been designed for an active/active setup, rather for a master-slave setup.
Lsyncd does not sync the entire tree every time. It depends on the situation, most of the time in our use case it starts a rsync for 5 specific files. Only on startup or when the system is overloaded it syncs the entire tree.
