The SFlash is useful for when something might happen to your ps4 (some changes that affect the console in a way that it won't be able to boot later) and in case you need it you can use it together with your hardware flasher device to undo the changes you made to flash that caused the console to brick.
http://playstationhax.it/forums/topi...ot-ftp-server/
http://playstationhax.it/forums/topi...ot-ftp-server/