Presne tak. A rozdeleni na REDO-log a data postgresu taky neni cizi, viz dokumentace k write-ahead logu,
http://www.postgresql.org/docs/7.4/static/wal-internals.html
It is of advantage if the log is located on another disk than the main database files. This may be achieved by moving the directory pg_xlog to another location (while the server is shut down, of course) and creating a symbolic link from the original location in the main data directory to the new location.
A je to v postgresu uz delsi dobu, jen se mi nechtelo prohrabovat se starsimi manualy...