The operating system is
responsible for using hardware efficiently — for the disk drives, this means having a
fast access time and disk bandwidth.
Access time has two major components
Seek time is the time for the
disk are to move the heads to the cylinder containing
the desired sector.
Rotational latency is the additional
time waiting for the disk to rotate the
desired sector to the disk head.
Minimize seek time
Seek time » seek distance
Disk bandwidth is the total number of bytes transferred, divided
by the total time between the
first request for service and the completion of the last transfer.
Several algorithms exist to schedule the servicing of disk I/O requests.
We illustrate them with a request queue (0-199).
98, 183, 37, 122, 14, 124, 65, 67
Head pointer 53
