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Difficulty: HardResilient and Highly Available Storage Infrastructure

An energy utility provider runs a smart grid monitoring application on Amazon EC2 instances in an Auto Scaling group across multiple Availability Zones in the us-east-1 Region. The application requires a shared, POSIX-compliant file system to store active telemetry logs. Additionally, raw historical log files must be archived to a highly durable object store.

The provider wants to establish a disaster recovery (DR) architecture in the us-west-2 Region with a Recovery Time Objective (RTO) of 15 minutes and a Recovery Point Objective (RPO) of 15 minutes for both active logs and historical archives. Historical archives must be accessible within minutes during a DR event.

Which two configurations should the solutions architect implement to meet these requirements?

  1. Configure Amazon EFS replication to automatically replicate the shared file system from us-east-1 to us-west-2.Answer
  2. Store raw historical logs in an Amazon S3 bucket in us-east-1, and configure Cross-Region Replication (CRR) with S3 Replication Time Control (S3 RTC) enabled to a destination bucket in us-west-2.Answer
  3. C
    Store raw historical logs in Amazon S3, and configure a replication rule to copy the objects to a destination bucket in us-west-2 with the S3 Glacier Flexible Retrieval storage class.
  4. D
    Migrate the shared telemetry logs to an Amazon RDS Multi-AZ DB instance in us-east-1, and configure a cross-region Read Replica in us-west-2 to act as the automated, zero-administrative failover endpoint.
  5. E
    Implement a Pilot Light disaster recovery strategy by creating daily Amazon Machine Images (AMIs) of the EC2 instances and daily backups of the shared storage, copying them to us-west-2, and restoring them during a failover event.

Answer

Configure Amazon EFS replication to automatically replicate the shared file system from us-east-1 to us-west-2, and store raw historical logs in an Amazon S3 bucket in us-east-1, configuring Cross-Region Replication (CRR) with S3 Replication Time Control (S3 RTC) enabled to a destination bucket in us-west-2.
To satisfy a POSIX-compliant shared file system requirement with a 15-minute RTO and RPO in a secondary region, Amazon EFS replication is the correct choice because it automatically and continuously replicates changes to the destination region within minutes. To satisfy the raw historical logs archiving requirement with a 15-minute RPO, Amazon S3 Cross-Region Replication with S3 Replication Time Control (S3 RTC) is the correct choice because it provides a service level agreement (SLA) to replicate 99.9% of objects within 15 minutes, and storing them in standard S3 buckets ensures they are immediately accessible during a failover event.

Step-by-Step Solution

1
Analyze the file system requirement and RTO/RPO limits.
The application requires a POSIX-compliant shared file system. Amazon EFS provides this capability for EC2 instances. To meet the 15-minute RTO and RPO in the us-west-2 DR region, Amazon EFS replication is required as it replicates data within minutes.
Identify the primary storage service that supports shared POSIX access and cross-region replication within minutes.
2
Analyze the historical log archiving requirement and RTO/RPO limits.
Historical logs must be stored in a highly durable object store (Amazon S3). To meet the 15-minute RPO, S3 Cross-Region Replication (CRR) with Replication Time Control (S3 RTC) must be configured, which guarantees replication of 99.9% of objects within 15 minutes. To meet the 15-minute RTO, the target storage class must allow rapid access (milliseconds/minutes).
Identify the object storage replication and retrieval configuration that satisfies the RTO and RPO criteria.
3
Evaluate and eliminate incorrect architectures.
Using S3 Glacier Flexible Retrieval for replicated archives introduces retrieval delays of 3-5 hours, violating the RTO. Daily backups (Pilot Light) violate the 15-minute RPO. Relying on RDS Read Replicas does not solve the shared file system requirement and lacks automated cross-region failover.
Ensure all other options are eliminated based on AWS service limitations and scenario constraints.

Key Concept

Designing highly available, multi-region storage systems using EFS Replication and S3 Replication Time Control (RTC) to meet strict RTO and RPO requirements.
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Topics

Resilient and Highly Available Storage Infrastructure

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