Figure 5: Performance of SCAN scheduling for the organ-pipe arrangement of data and random allocation of memory among tracks. The benefits of the organ-pipe arrangements are mild but consistent. For the plot  cm,  cm,  cm/ms, the disk spins at 7200 RPM, and each request is for 50 cm of physical track length. For under organ-pipe we use a quadratic which peeks at and vanishes at the extremal tracks.