What is "fscan"

FScan is a disk scheduling algorithm to determine the motion of the disk's arm and head in servicing read and write requests. It uses two subqueues. During the scan, all of the requests are in the first queue and all new requests are put into the second queue. Thus, service of new requests is deferred until all of the old requests have been processed. When the scan ends, the arm is taken to the first queue entries and is started all over again.