SA PRO- Review mode set 1 question 7.

[khawaja]

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Q. An online immigration system is currently hosted on one large EC2 instance with EBS volumes to store all of the applicants’ data. The registration system accepts the information from the user including documents and photos and then performs automated verification and processing to check if the applicant is eligible for immigration. The immigration system becomes unavailable at times when there is a surge of applicants using the system. The existing architecture needs improvement as it takes a long time for the system to complete the processing and the attached EBS volumes are not enough to store the ever-growing data being uploaded by the users.

Which of the following is the best option to achieve high availability and a more scalable data storage?

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The option that says: Upgrade your architecture to use an S3 bucket with cross-region replication (CRR) enabled, as the storage service. Set up an SQS queue to distribute the tasks to a group of EC2 instances with Auto Scaling to dynamically increase or decrease the group of EC2 instances depending on the length of the SQS queue. Use CloudFormation to replicate your architecture to another region is correct because it provides high availability and scalable data storage with S3. Auto-scaling of EC2 instances reduces the overall processing time and SQS helps in distributing the tasks to a group of EC2 instances.

The option that says: Upgrade to EBS with Provisioned IOPS as your main storage service and change your architecture to use an SQS queue to distribute the tasks to a group of EC2 instances. Use Auto Scaling to dynamically increase or decrease the group of EC2 instances depending on the length of the SQS queue is incorrect because an EC2 instance store is ephemeral storage and should never be your choice in storing user data. You should use S3 instead.

The above option talks about EBS volumes but the explanation says EC2 instance store is an ephemeral storage. The explanation does not seem right. Also this option seems correct for this question.

Could someone please provide further explanation on this?

• This discussion was modified 2 years, 8 months ago by  khawaja.

[Kenneth-Samonte-Tutorials-Dojo]

Hi khawaja,

Thank you for sharing your feedback on this question.

I agree that the explanation for the incorrect answer is not very clear. I will revise it to properly explain the situation.

The main problem with this question is that it is a single large EC2 instance and the attached EBS volumes are not enough to store the growing data from users.

Therefore, as best practice recommended by AWS, for static content or objects that need to have durable and highly scalable we should choose Amazon S3 for storage.

You are correct that EBS volumes are persistent storage and the EC2 instances are not using Ephemeral storage. Still, using EBS volumes and Autoscaling group of EC2 instances have disadvantages.

For example, if your total storage requirement is 1TB, then all EC2 instances must have a 1TB EBS volume attached to them. The cost will increase with each EC2 instance that is provisioned by the Auto Scaling group. Also, what if the storage requirement is now 2TB, then all EC2 instances must have a bigger EBS volume again. There is no automated way to dynamically increase the EBS volumes of the EC2 instances and it is not very economical to have large EBS volumes to each EC2 instance. Also since the data is growing, it will be harder to sync the data between the EBS volumes of the Auto scaling group.

For this situation, Amazon S3 serves the purpose of storing all the data, storage is virtually unlimited, highly available (with 99.999999999% durability), and is very cheap compared to EBS volumes.

Hope this helps.

Let us know if you need further assistance. The Tutorials Dojo team is dedicated to helping you pass your AWS exam!

Regards,

Kenneth Samonte @ Tutorials Dojo