Solved Examples on Rotational Latency
Example: Calculate the average rotational latency if disk rotation is 6000 RPM.
Solution:
6000 rotations in 60 sec
1 rotation = 60 / 6000 sec
1 rotation = 10 msec
Average rotational latency = Time for 1 rotation / 2
Average rotational latency = 10 msec / 2
Average rotational latency = 5 msec
Example: Calculate the average rotational latency if disk rotation is 3000 RPM.
Solution:
3000 rotations in 60 sec
1 rotation = 60 / 3000 sec
1 rotation = 20 msec
Average rotational latency = Time for 1 rotation / 2
Average rotational latency = 20 msec / 2
Average rotational latency = 10 msec
Example: Calculate the average rotational latency if disk rotation is 1200 RPM.
Solution:
1200 rotations in 60 sec
1 rotation = 60 / 1200 sec
1 rotation = 50 msec
Average rotational latency = Time for 1 rotation / 2
Average rotational latency = 50 msec / 2
Average rotational latency = 25 msec
Example: Calculate the average rotational latency if disk rotation is 2400 RPM.
Solution:
2400 rotations in 60 sec
1 rotation = 60 / 2400 sec
1 rotation = 25 msec
Average rotational latency = Time for 1 rotation / 2
Average rotational latency = 25 msec / 2
Average rotational latency = 12.5 msec
Example: Find the rotational latency of the disk if the angle between current sector and desired sector is 60 degrees and rotational frequency is 10 MHz.
Solution:
Angle between current sector and desired sector = 60°
Rotational frequency = 10 MHz
Rotational latency = (angle between current sector and desired sector) / Rotational frequency
Rotational latency = 60 / 10 MHz
Rotational latency = 6 microseconds
Example: Find the rotational frequency of the disk, given the angle between the current and the desired sector is 30 and rotational latency is 10 ns.
Solution:
Angle between current sector and desired sector = 30°
Rotational Latency = 10 ns
Rotational latency = (angle between current sector and desired sector) / Rotational frequency
Rotational frequency = 30 / 10 ns
Rotational frequency = 3 GHz
Rotational Latency
The time required by the read/write head to move from the current sector to the desired sector is called the rotational latency. The rotational latency can be calculated by dividing the angle between the current sector and the desired sector by the rotational frequency.
The formula for calculating the rotational latency is given by:
Rotational latency = (angle between current sector and desired sector) / Rotational frequency
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