238 views

A hard disk system has the following parameters:

• Rotation speed – $6000$ rpm.
• Size of each sector – $1$ KB.
• Average number of sectors per track – $128$.

Based on these parameters, which of the following statements is/are CORRECT?

1. The average latency of the drive is less than $6$ milliseconds.
2. The burst data rate of the drive is more than $10$ MB/sec.
3. The average capacity per track is larger than $1$ MB.
1. I only
2. I and III only
3. I and II only
4. I, II, and III

1. Average rotational latency in hard drive is

(1 / (RPM / 60)) * 0.5 * 1000  ms

Or, (30000 / RPM)  ms = 30000 / 6000 = 5 ms , this makes statement I correct .

2. The burst data rate is  average track capacity * rotations per second = 128 * 0.001 * 100 MB/sec = 12.5 MB per second ( as 1 KB = 0.001 MB ) , this makes statement II correct.

3. The average capacity of each track is average number of sectors per track *  the size per sector = (128 * 1) KB =128 KB, which makes statement III false .

So, only statement I and II are correct , which is option C .
by

I too not agreed with this,

Average seek time = 2 * average latency

how this happens??

1 vote