In order to minimize the seek time it first serves all requests in one
direction until it does not have any requests in this direction anymore. The head movement is then reversed and service is continued. SCAN provides a very good seek time because the
edge tracks get better service times. Note that middle tracks still get a better service than edge tracks. When the head movement is reversed, it first serves tracks that have recently
been serviced , where the heaviest density of requests, assuming a uniform disrtibution, is at the other end of the disk.
