DVA-C02 practice question 1 of 35

A company has a multi-node Windows legacy application that runs on premises. The application uses a network shared folder as a centralized…

Domain Security

A company has a multi-node Windows legacy application that runs on premises. The application uses a network shared folder as a centralized configuration repository to store configuration files in .xml format. The company is migrating the application to Amazon EC2 instances. As part of the migration to AWS, a developer must identify a solution that provides high availability for the repository. Which solution will meet this requirement MOST cost-effectively?

Answer options

A: Mount an Amazon Elastic Block Store (Amazon EBS) volume onto one of the EC2 instances. Deploy a file system on the EBS volume. Use the host operating system to share a folder. Update the application code to read and write configuration files from the shared folder.

B: Deploy a micro EC2 instance with an instance store volume. Use the host operating system to share a folder. Update the application code to read and write configuration files from the shared folder.

C: Create an Amazon S3 bucket to host the repository. Migrate the existing .xml files to the S3 bucket. Update the application code to use the AWS SDK to read and write configuration files from Amazon S3. Correct answer

D: Create an Amazon S3 bucket to host the repository. Migrate the existing .xml files to the S3 bucket. Mount the S3 bucket to the EC2 instances as a local volume. Update the application code to read and write configuration files from the disk.

Correct Answer:

C. Create an Amazon S3 bucket to host the repository. Migrate the existing .xml files to the S3 bucket. Update the application code to use the AWS SDK to read and write configuration files from Amazon S3.

Explanation

Amazon S3 is an object storage service designed for high availability and 99.999999999% (11 nines) of durability by redundantly storing data across multiple Availability Zones. This makes it an ideal, highly available repository for configuration files. By updating the application to use the AWS SDK, the EC2 instances can directly and concurrently access the configuration files from the S3 bucket. This serverless approach is the most cost-effective as it eliminates the need to provision and manage dedicated EC2 instances or block storage for a file server, and you only pay for the S3 storage and requests made.

Why Incorrect

A. This solution creates a single point of failure. If the EC2 instance hosting the EBS share fails, the entire application loses access to its configuration, violating the high availability requirement.
B. Instance store is ephemeral and not persistent. Any data on an instance store volume is lost if the instance is stopped or terminated, making it unsuitable for a configuration repository.
D. Mounting an S3 bucket as a local volume adds a layer of abstraction (e.g., using s3fs-fuse) that can introduce performance and consistency complexities compared to native SDK calls, making it a less optimal solution.

References

1. Amazon S3 Features: The official documentation states

"Amazon S3 is designed for 99.999999999% (11 9's) of durability

and stores data for millions of applications for companies all around the world... S3 Standard is designed for 99.99% availability over a given year." This supports its use for a highly available repository.

Source: AWS Documentation

"Amazon S3 Features

" section on "Durability and data protection."

2. Amazon EC2 Instance Store: The documentation clarifies the non-persistent nature of instance stores: "The data in an instance store persists only during the life of its associated instance. If an instance reboots (intentionally or unintentionally)

data in the instance store persists. However

data in the instance store is lost under any of the following circumstances: The underlying drive fails

The instance stops

The instance hibernates

The instance terminates."

Source: AWS Documentation

"Amazon EC2 User Guide for Linux Instances

" section "Amazon EC2 instance store."

3. Amazon EBS Volumes: The documentation explains that a standard EBS volume is attached to a single instance within a specific Availability Zone. "An Amazon EBS volume is a durable

block-level storage device that you can attach to a single EC2 instance." This confirms that sharing it from one instance (as described in option A) makes that instance a single point of failure.

Source: AWS Documentation

"Amazon EC2 User Guide for Linux Instances

" section "Amazon EBS volumes."

4. Accessing S3: The AWS SDK Developer Guides provide the canonical method for applications to interact with S3. "The AWS SDK for [Language] provides an API for the Amazon S3 bucket and object operations." This confirms that using the SDK is the intended and direct method for programmatic access.

Source: AWS Documentation

"AWS SDK for .NET Developer Guide

" section "Amazon S3 examples."

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