Anything-sync-daemon (asd) is a is a diminutive pseudo-daemon designed to manage target directories in tmpfs and to periodically sync them back to your physical disc (HDD/SSD). This is accomplished via a symlinking step and an innovative use of rsync to maintain back-up and synchronization between the two. One of the major design goals of asd is a completely transparent user experience.
https://wiki.archlinux.org/index.php/Anything-sync-daemon#Edit_.2Fetc.2Fasd.conf