In a very large mixing bowl combine half-and-half or light cream, sugar, and vanilla. Stir until sugar is dissolved. Stir in whipping cream. Stir in chopped peaches and toasted pecans.
Freeze in a 4- or 5-quart ice-cream freezer according to manufacturer's directions. Remove dasher. Repack outer freezer bucket with ice and salt and ripen for about 4 hours. Garnish with peach slices, if desired. Makes 2 quarts (16 servings).