Elevator algorithm

The elevator algorithm, also called SCAN, is a disk-scheduling algorithm that decides how the arm and head of a disk drive move while servicing read and write requests. It is named after the behavior of a building elevator, which keeps travelling in its current direction until it is empty, stopping only to let people off or to pick up new passengers heading the same way. In implementation, the drive keeps a buffer of pending requests together with the cylinder number of each, where lower cylinder numbers are nearer the spindle and higher numbers are farther away. The algorithm is now largely obsolete for data storage, because current magnetic disks hide the physical location of data and solid state memory has a seek time that does not depend on location.