A 3-tier e-commerce web application is currently deployed on-premises and will be migrated to AWS for greater scalability and elasticity. The web server currently shares read-only data using a network distributed file system. The app server tier uses a clustering mechanism for discovery and shared session state that depends on IP multicast. The database tier uses shared-storage clustering to provide database failover capability and uses several read replicas for scaling. Data on all servers and the distributed file system directory is backed up weekly on a separate backup server. Which of the following AWS storage and database architectures meets the requirements of the application?

Answer options:

A.Web servers store read-only data in S3, and copy it from S3 to root volume at boot time. App servers share state using a combination of DynamoDB and IP unicast. Database use RDS with multi-AZ deployment and one or more Read Replicas. Backup web and app servers weekly via snapshots. Use the snapshots to create the AMIs ( data copied to EC2 instances from the dedicated backup servers ). Back up the database via DB snapshots.
B.Web servers store read-only data in S3, and copy it from S3 to root volume at boot time. App servers share state using a combination of DynamoDB and IP unicast. Database use RDS with multi-AZ deployment and one or more Read Replicas. Backup web servers, app servers, and database weekly to Glacier using snapshots.
C.Web servers store read-only data in S3 and copy it from S3 to root volume at boot time. App servers share state using a combination of DynamoDB and IP unicast. Database use RDS with multi-AZ deployment. Backup web and app servers weekly via AMIs. Back up the database via DB snapshots.
D.Web servers store read-only data in an EC2 NFS server and mount to each web server at boot time. App servers share state using a combination of DynamoDB and IP multicast. Database use RDS with multi-AZ deployment and one or more Read Replicas. Backup web and app servers weekly via AMIs, and back up the database via DB snapshots.

Answer - A
The main requirements of this scenario are: (1) the application should be scalable and elastic, (2) app servers should be able to share the state, (3) need read replicas, and (4) weekly backup of the data.
Option A is CORRECT because (a) the overall architecture is highly available, elastic, and scalable, (b) web servers share state using DynamoDB and IP unicast that is supported by AWS, (c) it supports read replicas, and (d) weekly backup for servers using AMIs and data using DB snapshots.
Option B is incorrect because you cannot backup data to Glacier using snapshots.
Option C is incorrect because it does not address the requirement of having read replicas for elasticity and scalability.
Option D is incorrect because it is not suitable to store the read-only data in EC2. S3 should be selected as it is a more available and durable storage service.
For more information on this topic, please visit the link below.
https://d0.awsstatic.com/whitepapers/Storage/AWS%20Storage%20Services%20Whitepaper-v9.pdf