Editing Elevator algorithm (section)

{{Short description|Disk-scheduling algorithm}}
{{Refimprove|date=November 2007}}

The '''elevator algorithm''', or '''SCAN''', is a [[hard disk|disk]]-[[I/O scheduling|scheduling]] algorithm to determine the motion of the disk's arm and head in servicing read and write requests.

This algorithm is named after the behavior of a building [[elevator]], where the elevator continues to travel in its current direction (up or down) until empty, stopping only to let individuals off or to pick up new individuals heading in the same direction.  

From an implementation perspective, the [[disk drive|drive]] maintains a [[data buffer|buffer]] of pending read/write requests, along with the associated [[Cylinder (disk drive)|cylinder]] number of the request, in which lower cylinder numbers generally indicate that the cylinder is closer to the spindle, and higher numbers indicate the cylinder is farther away.