I wish SD cards would implement a key-value storage interface natively. It would instantly remove the need to implement a filesystem in many embedded systems eg. music players: all they need is access to keys (song filenames) and values (blob of ogg/mp3 data).
The most famous ways of managing configuration is serializing a structure on EEPROM/Flash, or writing a string with lengths of the strings as delimiters.
Even if you assume, its for saving space etc. The way I see you will inevitably use space while you write the code to serialize and de serialize the configuration data.