GATE - 2005 | OS | A disk has 8 equidistant tracks. The diameters of the innermost and

GATE - 2005 [Operating System]

Question:

A disk has 8 equidistant tracks. The diameters of the innermost and outermost tracks are 1 cm and 8 cm respectively. The innermost track has a storage capacity of 10 MB. What is the total amount of data that can be stored on the disk if it is used with a drive that rotates it with (i) Constant Linear Velocity (ii) Constant Angular Velocity?  

A	(i) 80 MB (ii) 2040 MB
B	(i) 2040 MB (ii) 80 MB
C	(i) 80 MB (ii) 360 MB
D	(i) 360 MB (ii) 80 MB

Solution:

Option (D) is Correct.

Constant linear velocity:
Diameter of inner track = d = 1 cm
Circumference of inner track
= 2 * 3.14 * d/2
= 3.14 cm

Storage capacity = 10 MB (given)
Circumference of all equidistant tracks
= 2 * 3.14 * (0.5+1+1.5+2+2.5+3+3.5+4)
= 113.14 cm

Here, 3.14 cm holds 10 MB
Therefore, 1 cm holds 3.18 MB.
So, 113.14 cm holds
113.14 * 3.18 = 360 MB
So, total amount of data that can be hold on the disk = 360 MB.

For constant angular velocity:
In case of CAV, the disk rotates at a constant angular speed.

Same rotation time is taken by all the tracks.
Total amount of data that can be stored on the disk
= 8 * 10 = 80 MB

Thank You