SCAN or Elevator
• The disk arm starts at one end of the disk, moves
toward the other end, servicing requests until
reaching end of disk, then the head reverses and
servicing continues.
– i.e. Pick the closest request in same direction as last
arm motion
• Con – more arm motion than SSTF
• Pro
– Fair
– Avoids starvation
• Example total head movement of 208 cylinders.