McIlroy has edge in Dubai
It was advantage Rory McIlroy with nine holes to play in the European Tour's season-ending DP World Tour Championship.
Already with the Tour's money list title in the bag, the 23-year-old started for home 18 under par, with Donald one behind and England's Justin Rose and South African Louis Oosthuizen two back.
Earlier Spain's Sergio Garcia equalled the course record of 64 for the second time in the week. He eagled the par five 18th again to do it, while Scot Stephen Gallacher and Dutchman Joost Luiten had holes-in-one at the fourth and sixth respectively.
The world number one resumed tied for the lead with Luke Donald and it was the world number two who started the better, grabbing a birdie on the long second after McIlroy had pushed his opening drive and bogeyed.
But then came Donald's first bogey not only of the tournament, but his first in 103 holes on the course, when he three-putted the third.
McIlroy birdied the fifth and seventh, had another bogey at the next, but closed the outward half with a brilliant approach to two feet.