Question

An application loads 100 libraries at startup. Loading each library requires exactly one disk access. The seek time of the disk to a random location is given as 10 ms. Rotational speed of disk is 6000 rpm. If all 100 libraries are loaded from random locations on the disk, how long does it take to load all libraries? (The time to transfer data from the disk block once the head has been positioned at the start of the block may be neglected.)
1. 0.50 s
2. 1.50 s
3. 1.25 s
4. 1.00 s

Answer 1

Correct Answer - Option 2 : 1.50 s

The correct answer is option 2

Data:

Seek time = 10 ms

Rotational speed = 6000 rpm

Transfer time has given negligible

total 100 files are loaded from the disk

Formula:

Disk access time = Seek time + Rotational latency + Transfer time

Calculation:

Rotational speed = 6000 rpm

6000 rotation → 60s

1 rotation → \({60\over6000}s\)

1 rotation → 10 ms

Average rotational delay = 10 ÷ 2 = 5 ms

Disk access time = seek time + Rotational latency + transfer time(given negligible)

Disk access time = 10 ms + 5ms + 0 = 15 ms

Now, total time to transfer one library → 15 ms

So, the total time to transfer 100 libraries → 100 × 15ms =1.5s