2,182 views
1 votes
1 votes

A disc drive has a average seek time of 10ms, 32 sectors on each track and 512 bytes per sector.
If the average time to read 8kbytes of continuously stored data is 20ms, what is the rotational speed of the disc drive?

  1. 3600 rpm
  2. 6000 rpm
  3. 3000 rpm
  4. 2400 rpm

1 Answer

2 votes
2 votes
Let, 1 rotation take x ms to complete.

Now, Total capacity of each track = 32 * 512 B = 16 KB

Therefore, 16 KB data is transmitted in x ms.

Therefore, 1 B data is transferred in (x / 16K) ms.

Therefore, 8 KB data is transferred in (8 K x / 16 K) ms = (x / 2) ms

Transfer Time = (x / 2) ms

Now, we know that

Avg. Read Time = Seek Time + Rotational Latency + Transfer Time

Further, Rotational Latency = Rotation Time / 2 = (x / 2) seconds

Therefore, 20 ms = 10 ms + (x / 2) ms + (x / 2) ms

On solving the above equation, we get

x = 10 ms

This means that in 10 ms, the disk rotates 1 time.

Therefore, in 1 s, the disk rotates 100 times.

Therefore, in 60 s, i.e. 1 min, the disk rotates 6000 times.

Therefore, the rotational speed is 6000 rpm.

Related questions

0 votes
0 votes
0 answers
1
GATE SPY asked Jan 15, 2019
373 views
A perfect cubic dice thrown a large number of times in a set of 8.The occurrence of 5 or 6 is called a success in what proportion of sets would you expect 3 successes?
2 votes
2 votes
3 answers
3