Why was "tantrum" trending last week?
A variation of the Scan disk aceess algorithm for use in a real-time environment where, in general, requests are served according to Earliest Deadline First. If two requests share the same deadline, they may be reorganised according to Scan.
A typical example is a video server that retrieves video data from a hard disk. The playback of a video impose tight real-time constraints but if the server retrieves data once every second for each video channel, Scan-EDF can be applied, reducing the seek overhead.