SHORT ANSWER QUESTIONS

1. [ 2 marks ] Why are CD-ROM seeks so slow compared to magnetic disks?
2. [ 2 marks ] What does "head settle time" mean and to what kind of device does it refer?

LONG QUESTIONS

1. (worth 15 total) How do Optical Compact Disks differ from Magnetic Disks (physically and in terms of access and file management).
   
   
2. (worth 10 total) For each pair of devices below, name or describe a situation (or application) where you would choose the first over the second and one where the choice is reversed.
   A. Pereos vs. DAT
   B. CD-ROM vs. DVD
   C. Zip vs. Jaz
   D. RAID vs. 'regular' HD (like a Cheetah)
   E. Floppy(s) vs. CD-ROM
   
   
3. (worth 15 total) For each category of devices, name 1 thing that distinguishes it from all others and list and explain at least 1 advantage and disadvantage of this device compared to all others.
   a)Tape Devices
   b)CD-ROM
   c)RAID
   
   
4. (worth 25 total)

   Disk Specs:	Ave. Seek time:	20 ms.
   	Ave. Rotational Delay:	5 ms.
   	Transfer Rate:	1 Megabyte / sec.

   
   

   Tape Specs:	Recording Density:	1600 bytes/inch
   	Interblock Gaps:	0.5 inches
   	Transfer Speed:	50 inches/sec.
   	Start/Stop Time:	0.01 sec. (each)

   The FILE is 4 Megabytes in size and the block size (for both disk and tape) is 1000 bytes (as opposed to 1Kb).
   
   a) [5] What is the average access time on the disk?
   b) [2] What % of the total access time is used in positioning the head over the start of the block?
   c) [2] What % of the total access time is used for seek and delay if we use a fixed head disk?
   d) [6] How long will it take to transfer a 4 Megabyte file using the disk (assume the program is I/O bound)? {2 answers: 1. If transfer is uninterrupted; 2. If heads are moved after each block transfer }
   e) [5] How much tape do we need to store this file on tape?
   f) [5] How long will it take to transfer a 4 Megabyte file using the tape (discount processing time)?
   
5. (worth 15 total) For each category of devices, name one thing that distinguishes it from all other devices (not just the ones listed). Then identify and explain at least one advantage and disadvantage of this device compared to all others.
   
   A. RAID system
   B. Magneto-Optical Disk (writeable)
   C. Superdisk
   
   
6. (worth 10 total)
   For each of the following situations or data sets name the mass storage device you think would be most appropriate. Briefly explain why. (Be specific; e.g. DAT rather than just magnetic tape).
   
   a) a 300 Megabyte application program being sold commercially
   b) a very large (15GB) database that is in use almost continuously
   c) Revenue Canada's tax records from 1997
   d) Revenue Canada's tax records from 1988
   e) incremental dumps (backup) for a small company whose computer system consists of a small LAN made up entirely of PC's
   
   
7. (worth 15 total)
   For each situation, describe what kind of secondary storage you would recommend and explain why you would recommend it.