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Which of the following will meet your requirements?

You have a distributed application that periodically processes large volumes of data across multiple Amazon
EC2 Instances. The application is designed to recover gracefully from Amazon EC2 instance failures. You are
required to accomplish this task in the most cost-effective way.
Which of the following will meet your requirements?

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A.
Spot Instances

B.
Reserved instances

C.
Dedicated instances

D.
On-Demand instances

27 Comments on “Which of the following will meet your requirements?

  1. T says:

    A – Spot instances are the cheapest but they can be taken away by AWS to another customer who pays more. As as the application is designed to recover gracefully from Amazon EC2 instance failures, we should use Spot instances as they are the cheapest.




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  2. R says:

    D

    Spot Instances are cheap, but the application runs periodically, what if they don’t get spot instances when application wants to write?




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    1. lol says:

      Answer is A. The clue is in the fact the application is designed to recover gracefully and we want to do it the most cost effective way. Spot instances would only be necessary if it wasnt designed to recover gracefully.




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  3. RP says:

    Answer must be “A” because The application is designed to recover gracefully from Amazon EC2 instance failures. Meaning of graceful: a delay allowed as a favour




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  4. Kelvin Wong says:

    My answer is A.

    The question says:

    “You have a distributed application that periodically processes large volumes of data across multiple Amazon EC2 Instances.” So we are assume that the application will occasionally need extra capacity and not what the application will entirely run on.




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  5. Senator says:

    I will go for “A”

    Looking at 2 key words in the question “most cost-effective way” and “recover gracefully”. Anytime you see “most cost-effective way” immediately think SPOT, then to confirm if it should be spot, check if it can recover as spot instances are pulled out anytime.




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  6. Srinivasu M says:

    Answer D:

    On-Demand instances are recommended for:
    Users that want the low cost and flexibility of Amazon EC2 without any up-front payment or long-term commitment
    Applications with short term, spiky, or unpredictable workloads that cannot be interrupted
    Applications being developed or tested on Amazon EC2 for the first time




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    1. donkeynuts says:

      The “Cannot be interrupted” here is the reason the answer is A.This specifically mentions the application can handle EC2 failures, which would happen when your spot instances are shut down. Im going for A here




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  7. g says:

    How can it be spot instances? Your bid price may not get the instance but you need to recover regardless. C is a distractor and Reserved instances are expensive for this purpose. D seems the only option




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    1. mutiger91 says:

      The other key in this question is that there is a large volume of processing across multiple instances. If you have one instance, go ahead and get the on-demand instance, because your time is worth too much to bother figuring out spot bidding. When you need to buy a lot of capacity you can write programs to acquire your instances based on all sorts of strategies.

      Spot is always cheaper on a unit cost basis for workloads that can terminate gracefully. It is cheaper on a TCO basis when the overhead of defining your bidding strategy is covered.




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  8. gman says:

    Test your application to ensure that it handles an unexpected instance termination gracefully. You can do so by running the application using an On-Demand instance and then terminating the On-Demand instance yourself.

    SPOT instance




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  9. Cuong says:

    B.
    Reserved instances

    I think we can use reserved instances since AWS allows to purchased scheduled reserved instance and our instances run periodically.

    Amazon EC2 Reserved Instance Options
    With Reserved Instances, you can choose the type of capacity reservation that best fits your application needs.

    Standard Reserved Instances: These instances are available to launch any time, 24 hours/day x 7 days/week. This option provides the most flexibility to run the number of instances you have reserved whenever you need them, including steady state workloads.
    Scheduled Reserved Instances: These instances are available to launch within the time windows you reserve. This option allows you to match your capacity reservation to a predictable recurring schedule that only requires a fraction of a day, a week, or a month. For example, if you have a predictable workload such as a monthly financial risk analysis, you can schedule it to run on the first five days of the month. Another example would be scheduling nightly bill processing from 4pm-12am each weekday.




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    1. vladam says:

      Using reserved instances is not the most cost-effective way.
      https://aws.amazon.com/blogs/aws/new-scheduled-reserved-instances/

      “Scheduled Reserved Instance model allows you to reserve instances for predefined blocks of time on a recurring basis for a one-year term, with prices that are generally 5 to 10% lower than the equivalent On-Demand rates.”

      You can get spot instances with much lower prices:
      https://aws.amazon.com/ec2/spot/pricing/

      “Spot instances are also available to run for a predefined duration – in hourly increments up to six hours in length – at a significant discount (30-45%) compared to On-Demand pricing plus an additional 5% during off-peak times for a total of up to 50% savings.”

      So A is correct answer.




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