Consider disk scheduling. Suppose a disk has 2000 cylinders, numbered 0 to 1999. The drive is currently serving a request at cylinder 80, and the...

Consider disk scheduling. Suppose a disk has 2000 cylinders, numbered 0 to 1999.  The drive is currently serving a request at cylinder 80, and the previous request was at cylinder 120.  The queue of pending requests, in FIFO order, is for blocks at cylinders:

            100

            1500

            800

            1800

            900

            1600

            1000

            1700

            200

Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk-scheduling algorithms?

• first-come-first-served

• shortest-distance-first

• SCAN (elevator algorithm, service requests in both directions, always move to the edge of the disk even if no requests are there )