Editing Elevator algorithm (section)

== Variations ==
One variation of this method ensures all requests are serviced in only one direction, that is, once the head has arrived at the outer edge of the disk, it returns to the beginning and services the new requests in this one direction only (or vice versa). This is known as the "Circular Elevator Algorithm" or C-SCAN.  Although the time of the return seek is wasted, this results in more equal performance for all head positions, as the expected distance from the head is always half the maximum distance, unlike in the standard elevator algorithm where cylinders in the middle will be serviced as much as twice as often as the innermost or outermost cylinders.

Other variations include:
* [[FSCAN]]
* [[LOOK algorithm|LOOK]]
** [[C-LOOK]]
* [[N-Step-SCAN]]

{| class="wikitable mw-collapsible"
! 
! SCAN
! LOOK
! C-SCAN
! C-LOOK
|-
! Repeated Motion 
| Goes to the last track (whether requested or not), then reverses direction and goes to the first track.
| Only goes as far as the final request in that direction, then reverses direction.
| Goes to the last track, then jumps to the first track and continues in the same direction.
| Only goes as far as the final request, then jumps to the first request and continues in the same direction.
|}