Lsyncd watches a local directory trees event monitor interface (inotify or fsevents). It aggregates and combines events for a few seconds and then spawns one (or more) process(es) to synchronize the changes.
CopyFS aims to solve a common problem : given a directory, especially one
full of configuration files, or other files that one can modify, and which
can affect the functionning of a system, or of programs, that may be important
to other users (or to the user himself), how to be sure that a person
modifying the files will do a backup of the working version first ?
This filesystem solves the problem by making the whole process transparent,
automatically keeping versionned copies of all the changes done to file under
its control.
It also allows a user to select an old version of the files, for example to
repair a mistake, and allows him/her to continue edition from this point.