For some reason my minidlna service run as "minidlna" user.
The default db /var/lib/minidlna/files.db is root:root 644.
and here is the wrong stuff :
1)The service scan dir to see if there is new files
2)Detect a new file "foobar" and try to add it to database
3)append to log file the unwritable database error
4)Jump to 1. With the same "foobar" file
So after hours my log file was 76Gb.
To fix this is think service should check the db for rw access and log once on errors.
Or log for every files present but log only once per file.
Of course i fix my installation by changing files.db to minidlna:minidlna 644 but i think fix the way the soft log is a better thing.