The Megatron 777 disk has the following characteristics Ther

The Megatron 777 disk has the following characteristics: There are ten surfaces, with 100, 000 tracks each. Tracks hold an average of 1000 sectors of 1024 bytes each. 20% of each track is used for gaps. The disk rotates at 10, 000 rpm. The time it takes the head to move n tracks is 1 + 0.0002n milliseconds. Answer the following questions about the Megatron 777. What is the capacity of the disk? If t racks are located on the outer inch of a 3.5-inch-diameter surface, what is the average density of bits in the sectors of a track? What is the maximum seek time? What is the maximum rotational latency? If a block is G5, 54G bytes (i.e., 64 sectors), what is the transfer time of a block?

Solution

a)

The capacity of the disk is calculated as follows:

Number of tracks=number of surfaces* number of tracks

The disk has 10*100,000=100,0000 tracks.

The average track has 1000*1024=1024,000 bytes. Thus, the capacity is 1.024 Gigabytes.

b)

If the tracks are located on the outer inch of a 3.5-inch diameter surface, the average density of bits in the sectors of a track is calculated as follows:

Average Density of bits in the sector of a track = (1000*1024*10) / ((3.5/2) * 3.14*80%)

= (1024 * 10^5) / (5.495*8)

= (1024 * 10^5) / (43.96)

= 23.2939*10^5

= 2.32939 M bits/ inch

c)

The maximum seek time:

Maximum Seek Time occurs when the heads must move across all the tracks. In the given formula 1+0.0002n, substitute n value = 100,000

Maximum Seek time = 1+0.0002(100,000/3)

Maximum Seek time = 1+6.66666666= 7.6666666ms

d)

Maximum rotational latency:

Maximum Rotational Latency is one full revolution. Here the disk rotates 10,000 rpm so maximum rotational latency is 1/ 10,000 of a minute.

Maximum Rotational Latency = 60 / 10,000

Maximum Rotational Latency = 6 milli second

e)

Transfer time of a block:

20% of each track is used for gap.64 sectors have 63 gaps

degrees = ((63/1000) *20% + (64/1000) *80%)*360⁰

= (0.126+0.0512) *360⁰ = 63.792⁰

Transfer time of a block = (degrees/ 360) *10

= (63.792⁰ /360) *10

= 1.772 ms