Calculate the sequential rate of I/O and the random rate of I/O, given the follo
ID: 3816873 • Letter: C
Question
Calculate the sequential rate of I/O and the random rate of I/O, given the following disk characteristics:
Average seek time (ms): 10 ms
Max Transfer rate (MB/s): 100 MB/s
Revolutions per minute (RPM): 7200 RPM
First, calculate average rotational latency:
Revolutions per minute (RPM): 7200 RPM
Revolutions per second (RPS): _______
Seconds per revolution (sec): _______
Average rotational latency: ________
Suppose the sequential workload is 100 MB:
Sequential I/O Time (T I/O) = Tseek + Trotation + Ttransfer
= ________ + ________ + __________
= __________
Rate Sequential I/O = Transfer Size / T I/O = ___________________________________________
Suppose the random workload is 4 KB:
Random I/O Time (T I/O) = Tseek + Trotation + Ttransfer
= ________ + ________ + __________
= __________
Rate Random I/O = Transfer Size / T I/O = ____________________________________________________
Explanation / Answer
Calculate the sequential rate of I/O and the random rate of I/O, given the following disk characteristics:
Average seek time (ms): 10 ms
Max Transfer rate (MB/s): 100 MB/s
Revolutions per minute (RPM): 7200 RPM
First, calculate average rotational latency:
Revolutions per minute (RPM): 7200 RPM
Revolutions per second(RPS): ____
Solution:
1 Revolution per minute is equal to 1/60 Hz
That is 0.0166666666666667.
Revolutions per second(RPS) = 0.0166666666666667 X 7200
=120.0000000000002 rps
Thus the value of Revolutions per second (RPS) is 120.0000000000002 rps
Seconds per revolution (sec): _______
Solution:
It can be calculated by the formula of 1/ Revolutions per second (RPS).
Seconds Per revolution (sec) = (1/120.0000000000002)
= 0.0083333333333333 sec
Thus the value of Seconds Per revolution is 0.0083333333333333 sec
Average rotational latency: ________
Solution:
It can be calculated by using the formula of Revolutions per minute multiply with 0.5 and multiply with 1000 Rotations.
Average rotational latency = (60/RPM)*0.5*1000
= (30000/RPM)
= 30000/7200
= 4.2 milliseconds
Thus the value of Average rotational latency is 4.2 milliseconds.
Suppose the sequential workload is 100 MB:
Solution:
Sequential I/0 Time can be calculated by using the sum of the values like Tseek ,
Trotation and Ttransfer.
Sequential I/O Time (T I/O) = Tseek + Trotation + Ttransfer
= 10 ms +120.0000000000002 rps + 100 MB/s
= 10 + 120.0000000000002 +100
= 230.0000000000002
Thus the values of Sequential I/O Time (T I/O) is 230.0000000000002
Rate Sequential I/O = Transfer Size / T I/O = ___________________________________________
Solution:
Rate of the sequential I/O Can be calculated by Transfer Size is divided by sequential I/O Time.
Rate of Sequential I/O = 100/230.0000000000002
= 0.4347826086956518
Thus the values of Rate of Sequential I/O is 0.4347826086956518
Suppose the random workload is 4 KB:
Random I/O Time (T I/O) = Tseek + Trotation + Ttransfer
Solution:
Random I/O Time can be calculated by using the sum of the values like T seek ,
T rotation and T transfer.
Random I/O Time (T I/O) = Tseek + Trotation + Ttransfer
= 10 ms +120.0000000000002 rps + 4 /1024 MB/s
= 130.0039062500002
Thus the values of Random I/O Time is 130.0039062500002
Rate Random I/O = Transfer Size / T I/O = ____________________________________________________
Solution:
Rate Random I/O Can be calculated by Transfer Size divided by Random I/O Time.
Rate of Random I/O = (4/1024)/ 130.0039062500002
= 0.00390625/130.0039062500002
= 3.00471740632793e-5
Thus the value Rate of Random I/O is 3.00471740632793e-5
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