MASTER OF COMPUTER APPLICATIONS
Course Code : MCS-012
Course Title : Computer Organisation and Assembly Language Programming
Assignment Number : MCA (2)/012/Assign /2014-15
Maximum Marks : 100
Weightage : 25%
What is rotational latency in the context of disk access time? Assume that the disk rotates at 6000 rpm; each track of the disk has 16 sectors; data transfer rate of the disk is 64 MB/second; and average seek time of disk is10 millisecond. Calculate the average access time for the disk.
Disk Rotation Speed = 6000 rpm
Sectors per Track = 16 sectors
Data transfer rate = 64 MB/second
Average seek time = 10 millisecond
Convertion is Shown Below:
Rotational latency = Average seek time + Average Rotational delay + Transfer time + Controller Overheads
Average seek time = 10 millisecond (given)
Calculate
Average Rotational delay = ½ Time of Rotation in milliseconds
Average Rotational delay = ½ * (60/6000) *1000 millisecond
= ½ * 10 millisecond
= 5 millisecond
Calculate
Transfer time = Block size / Transfer rate
Block size =? (Not Mentioned)
Assume = 1 KB per 1 sector
So 16 sector = 16 KB
Transfer time = (16 KB / 64 MB/sec)
= (16 / 64) millisecond
= 0.25 millisecond
Note:- Controller Overheads (optional) not using it For Now.
Rotational latency = Average seek time + Average Rotational delay + Transfer time
Rotational latency = 10 millisecond + 5 millisecond + 0.25 millisecond
= 10 + 5 + 0.25 millisecond
= 15.25 millisecond.