The distance between Ouarzazate and Marrakech is only 200km (125 miles) but the drive on the N9 through the High Atlas Mountains can take as long as four hours. The winding road, full of switch backs and featuring such scenery as to make one's jaw drop in disbelief is not recommended for those who suffer chronic motion sickness.
So, when we woke up, the long drive ahead of us and an eagerness to see my beloved Marrakech again, I medicated and prepared myself mentally for four hours of white-knuckle-torture.
By the time we arrived at this vantage point in the Tichka Pass, I was suffering more from a backache and pain in my hands than from nausea. Dramamine is truly a wonder drug! And thank god for it, there isn't a drive I have done anywhere in the world that was as rewarding as the road from Ouarzazate to Marrakech.
Car rental is possible and the Lonely Planet forums have great information on doing this yourself but I recommend having a very good, local driver. Be prepared with very warm clothing for getting out and taking pictures at the highest parts of the pass, the temperature drop is astonishing and the winds will knock you over. The view you're rewarded with is, of course, worth it! There are also wonderful small villages scattered all along the N9 - to stop in and eat, shop and rest your body before completing the drive.