Physical Standby Database and standy_archive_dest parameter

 I have configured a physical stanby database on same host as the primary database .Now the standby_archive_dest path on the standby database is the same path as the log_archive_dest_n1 where the primary db archives the redo logs .This kind of configuration where Primary database is in maximum performance mode seems works fine and the archived logs files of he primary db aren't duplicated to trasmit to the standby db.So anywhere someone could explain me the mechanism to allow this kind of configuration (RFS process writes the redo data in the same path where the primary db archives)