Edit: just saw your other comment, so this may not apply to you now…Not that the default is smart, but the default has been set to fail a boot if parts are missing. Imagine a rocket launch system check, is temperature system online, no, fail and abort. While as users – for convenience–we want the system to boot even though a drive went offline, that may not be best default for induatrial applications. Or where another system relylies on first one to be up and coherent. So we have to use the nofail option, to contine the boot on missing drive.