In a large bowl, cream the butter, shortening and sugar until light and fluffy.
Beat in egg yolks and vanilla.
Combine flour and baking soda; add to creamed mixture alternately with buttermilk and beat just until combined.
Stir in coconut and pecans.
In a small bowl, beat egg whites until stiff peaks form.
Fold a fourth of the egg whites into batter, then fold in remaining whites.
Pour into three greased and floured 9-in. round baking pans.
Bake at 350° for 20-25 minutes or until a toothpick inserted near the center comes out clean.
Cool for 10 minutes before removing from pans to wire racks to cool completely.