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24556
March 29th, 2015 08:00
E10-001 Exam Question Query
Hello,
I greatly appreciate if you can you help me understand with explanation the answers to these four questions please. Thank you
An application generates 4200 small random I/Os at peak workloads with a read/write ratio of 2:1.
What is the disk load at peak activity for a RAID 5 configuration?
A. 2,800
B. 5,600
C. 8,400
D. 11,200
Answer: C
An application generates 4200 small random I/Os at peak workloads with a read/write ratio of 2:1.
What is the disk load at peak activity for a RAID 6 configuration?
A. 2,800
B. 5,600
C. 8,400
D. 11,200
Answer: D
An organization plans to deploy a new business application in their environment. The new
application requires 2 TB of storage space. During peak workloads, the application is expected to
generate 9,800 IOPS with a typical I/O size of 4 KB. Because the application is business-critical,
the response time must be within acceptable range.
The available disk drive option is a 15,000 rpm drive with 100 GB capacity. The number of IOPS in
which the disk drive can perform at 100 percent utilization is 140.
What is the number of disk drives needed to meet the application’s capacity and performance
requirements?
A. 20
B. 60
C. 70
D. 100
Answer: D (WHY ISN'T THIS ANSWER, C. 70)
An organization plans to deploy a new business application in their environment. The new
application requires 4 TB of storage space. During peak workloads, the application is expected to
generate 4900 IOPS with a typical I/O size of 8 KB. Because the application is business-critical,
the response time must be within acceptable range.
The available disk drive option is a 10,000 rpm drive with 200 GB capacity. The number of IOPS in
which the disk drive can perform at 100 percent utilization is 140.
What is the number of disk drives needed to meet the application’s capacity and performance
requirements?
A. 20
B. 25
C. 35
D. 50
Answer: D (WHY ISN'T THIS ANSWER, C. 35)
KEHutchinson
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March 30th, 2015 05:00
It would be helpful if you could show the work that you did on your calculations for these questions. Please explain what you currently understand about each one.
Willing
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30 Posts
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March 30th, 2015 15:00
Hi,
I now understand how the 1st two questions are answered once I converted the read/write ratio to a fraction then to decimal. That way I can calculate read ratio + write ratio x RAID write penalty for actual average required back-end IOPS.
However for the last 2 questions, I divided the required storage sizes by disk sizes and also the total size IOPS by the IOPS of each drive. The larger figure from the two calculations would be used. But the resulted figure isn't showed as correct?
KEHutchinson
2 Intern
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633 Posts
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April 7th, 2015 06:00
Can you show the calculations you used on these two questions? It will help others to see where there might be a problem.
Willing
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30 Posts
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April 10th, 2015 19:00
Hi Mike,
Thank you much for the info thus far.
2 questions:
Willing
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April 13th, 2015 10:00
Hi Mike,
They didn't cater for increased performance utilization (disk and disk controller utilization etc.) at peak workloads/peak times (faster response times) to cover entire SLA including business aspects. Safety net of .7 utilization is key. I now see how the original answers are correct
Thanks also for the info on the additional 25% aspect which I was not aware of. In addition it's good we can also leverage extended flash cash and flash to help optimize disk requirements from a performance perspective to name a few. Thanks again.
pavlos1
2 Posts
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May 29th, 2015 07:00
For questions 3 and 4. For acceptable response time, the disk controller utilization must be less than 70%. So if the IOPS are 140 on 100%, you have to find the number for 70%
100%=140
70%=98
So for question 3 the calculations are:
Storage - Available 100GB (How many do i need to reach 2TB),
100*20=2000 answer 20 disks
IOPS - Available 140 on 100%, 98 on 70%
98*100=9800 answer 100 disks
You take the biggest number from the two answers and this is the answer to the question.(100)
Same for question 4:
Storage - Available 200GB (How many do i need to reach 4TB),
200*20=4000 answer 20 disks
IOPS - Available 140 on 100%, 98 on 70%
98*50=4900 answer 50 disks
You take the biggest number from the two answers and this is the answer to the question.(50)
pavlos1
2 Posts
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June 2nd, 2015 09:00
And the equations for questions 1 and 2.
reads + (write penalty * writes)
4200 I/O with 2:1 read/write ratio means that 66.6% of 4200 are reads and 33.3% are writes
So 4200*66.6%=2800 I/O and 4200*33.3%=1400 I/O
Write penalty for RAID is:
RAID 1/0 = 2
RAID 5 = 4
RAID 6 = 6
So for question 1
=2800 + (4 * 1400)
=2800 + 5600
=8400
For question 2
=2800 + (6 * 1400)
=2800 + 8400
=11200