Homework Assignment 10

Homework Assignment 10

• Silberschatz et al, Operating System Concepts, 9th edition, Chapter 10, Mass Storage
  1. Suppose that a disk drive has 5,000 cylinders, numbered 0 to 4999. The drive is currently serving a request at cylinder 2150, and the previous request was at cylinder 1805. The queue of pending requests, in FIFO order, is:

     2069, 1212, 2296, 2800, 544, 1618, 356, 1523, 4965, 3681

     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?

     1. FCFS
     2. SSTF
     3. SCAN
     4. C-LOOK
     5. C-SCAN

  2. Consider a RAID Level 5 organization comprising five disks, with the parity for sets of four blocks on four disks stored on the fifth disk. How many blocks are accessed in order to perform the following?
     1. A write of one block of data
     2. A write of six continuous blocks of data

  3. If you have N disks of data, how many disks are required for:
     1. RAID 0
     2. RAID 1
     3. RAID 5