Wordpress metabox order data location

Wordpress makes it possible to drag & drop metaboxes. Where does wordpress save the data in which order the meta boxes must be rendered?

I know it fires a AJAX request to admin-ajax.php the moment you drop a metabox but I haven't got any further than that.

I could not find any documentation on it regarding the alteration or the functionality of the Javascript's Wordpress uses to do this.

I need to be able to retrieve the order of meta boxes per post. Each post can have it's own order of metaboxes.