The destination of uploaded images is selected automatically by existing data state of qa_blobs table. Therefor, there is no option said well in the admin panel. Lower buttons are equivalent to it if I say daringly. Because they are displayed exclusively, two buttons are the same as checkbox.
admin > stats > "Blobs to disk"
admin > stats > "Blobs to database"
When you enable QA_BLOBS_DIRECTORY of qa_config.php in empty state of qa_blobs, uploaded images are saved in the file system, not qa_blobs.