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Difficulty: EasyHigh Availability and Disaster Recovery Design

A company is designing a disaster recovery (DR) strategy for its internal HR portal. The application runs on Amazon EC2 instances behind an Application Load Balancer in a Multi-AZ configuration, using an Amazon RDS for PostgreSQL database. The business requires a Recovery Time Objective (RTO) of 4 hours and a Recovery Point Objective (RPO) of 24 hours. The solutions architect must design a cost-effective solution that minimizes ongoing idle resource costs. Which two actions should the solutions architect take to meet these requirements?

  1. Configure daily automated backups of the Amazon RDS database and copy the snapshots to a secondary AWS Region.Answer
  2. Store the application server configuration as an Amazon Machine Image (AMI), copy the AMI to a secondary AWS Region, and maintain an AWS CloudFormation template to provision the application infrastructure in the secondary Region only during a disaster.Answer
  3. C
    Deploy a cross-region Amazon RDS Read Replica in the secondary AWS Region and configure Amazon Aurora Replica Auto Scaling to dynamically adjust replica capacity.
  4. D
    Configure a Route 53 Private Hosted Zone for the portal in the secondary Region's VPC without associating it with the primary Region's VPC, relying on default cross-VPC DNS inheritance.
  5. E
    Deploy a single NAT Gateway in one Availability Zone in the primary Region and route all outbound internet traffic from all private subnets through it to reduce gateway hourly charges.

Answer

Configure daily automated backups of the Amazon RDS database and copy the snapshots to a secondary AWS Region, and store the application server configuration as an Amazon Machine Image (AMI), copy the AMI to a secondary AWS Region, and maintain an AWS CloudFormation template to provision the application infrastructure in the secondary Region only during a disaster.
The correct strategy combines daily database snapshots copied to a secondary region with on-demand infrastructure provisioning using AMIs and CloudFormation. Since the database is backed up daily, the 24-hour RPO is met. Restoring the database from a snapshot and deploying the application tier using CloudFormation can easily be completed within the 4-hour RTO. This minimizes ongoing idle costs since no compute or database resources run in the secondary region during normal operations.

Step-by-Step Solution

1
Evaluate the RTO and RPO constraints against the disaster recovery options.
An RTO of 4 hours and RPO of 24 hours can be achieved using a cost-effective Backup and Restore strategy, which does not require active resources to run in the secondary region.
This step determines the most appropriate DR pattern to meet the customer's cost-efficiency goal.
2
Determine the database backup and transfer strategy.
Daily snapshots meet the 24-hour RPO requirement, and copying them to a secondary region ensures data durability without ongoing database instance costs.
This step secures the database data according to the RPO constraint.
3
Determine the compute tier restoration strategy.
Storing application server configurations as AMIs and using CloudFormation templates allows the environment to be constructed on-demand within the 4-hour RTO.
This step ensures that the compute resources can be deployed quickly during a disaster without incurring costs during normal operations.

Key Concept

For applications with non-critical RTO (hours) and RPO (24 hours or more), a Backup and Restore disaster recovery pattern is the most cost-effective solution. It avoids ongoing running costs in the recovery region by copying offline assets (database snapshots and AMIs) and deploying the environment using automation (CloudFormation) only when a failover is initiated.
Estimated Time:2m 0s
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Topics

High Availability and Disaster Recovery Design

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