You run a web application where web servers on EC2 Instances are In an Auto Scaling group Monitoring over
the last 6 months shows that 6 web servers are necessary to handle the minimum load During the day up to 12
servers are needed Five to six days per year, the number of web servers required might go up to 15.
What would you recommend to minimize costs while being able to provide hill availability?
A.
6 Reserved instances (heavy utilization). 6 Reserved instances {medium utilization), rest covered by OnDemand instances
B.
6 Reserved instances (heavy utilization). 6 On-Demand instances, rest covered by Spot Instances
C.
6 Reserved instances (heavy utilization) 6 Spot instances, rest covered by On-Demand instances
D.
6 Reserved instances (heavy utilization) 6 Reserved instances (medium utilization) rest covered by Spot
instances
The only plausible answer is A because all other answers include Spot Instances that can be removed without warning and that would not be highly available.
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Actually, this A and D are no longer valid, since as of December 2014 AWS does not sell Heavy, Medium or Light utilization. Therefore this question is also not valid.
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Good to know. I found many questions are outdated, we still need to use legacy settings to answer them.
So, I would go to A. because others use spotted instances, which is not acceptable.
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My second thought, B might be the answer, because the solution is required to “minimize cost”.
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Excluding the utilization type (which as Khozi pointed out is irrelevant now), A is the correct answer. Spot instances cannot be part of the answer because they are not guaranteed for availability.
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I wouldn’t agree with you Seth. There are couple of points I would like to point out. First, reserved instances requires agreement for a certain period, since the minimum servers that run most of time are 6 and may be 6 more servers on those exceptional days (5 to 6).
The reserved instances will be of waste resource if not utilized on another days. As they are not required to serve the traffic because the another six are capable of handling the load.
The solution for this B.
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Read the question properly. There are no periods(.) between sentances.
This is the condition
6- to run minimum load
another 6, – during the day
another 3 – 5 to 6 days a day
so minimum servers that run most of the time is 12.
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As long as you have proper health checks setup on your ELB and have instances that are not already spot, you should be ok with a few spot instances for web servers.
The answer is B IMHO.
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Five to six days per year, the number of web servers required might go up to 15.
What would you recommend to minimize costs while being able to provide hill availability?
spot doesn’t guarantee availability always – it can be pulled out anytime. Taking spot out of equation – we will be left out with A which is the correct answer.
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B
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I don’t go for any spot as availability not guaranteed.
So answer A.
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Spots are not guaranteed, how can you achieve high availability with that, so the answer shall be A.
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Options B is right. As they want 6 servers as fixed and more 6 that would require same configuration. And if any need spot instance will meet rest of requirement.
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Option B is right.
The question is ‘What would you recommend to minimize costs while being able to provide hill availability?’
‘minimize costs’ is also required.
‘venkat sai’ has pointed some valid arguments above already.
I would add that the point some of you have raised about spot instances can be pulled any time, doesn’t mean they ‘will’ be definitely removed on those rare days when they are required and also how much to bid for them is upto you as designer, so you can do a reasonable price bidding (above average) instead of lowest price.
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a
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Spot instances is not correct for this environment. The correct would be 6 reserved, 6 on-demands (working 50% of the time in a month) and the rest covered by on-demand too. But there is no option with this configuration. The more closer is A.
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B should be the Answer.
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B – spot is the cost minimization solution
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I have realized now that A is the correct answer, Spot instances are not viable at all for this solution.
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b
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B
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A
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C and D are Incorrect
A – Certainly provides availability but cost is high when compare to B
B is correct, since 12 instances are provide guaranteed availability and spot instances are used only during demand period, I see only the performance hit not the availability since there are 12 instance there to ensure app/web servers availability. So “B” best choice here considering “minimum cost” compare to A.
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I would go with B, because 12 reserved instances of A is ứate in almost times
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