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Difficulty: MediumResilient and Highly Available Storage Infrastructure

A financial services enterprise runs a real-time transaction reconciliation application on Amazon EC2 instances distributed across three Availability Zones. The application requires concurrent read/write access to a shared storage repository with high durability (99.999999999%99.999999999\%) and high availability (99.99%99.99\%). The storage architecture must support a Recovery Point Objective (RPO) of zero and a Recovery Time Objective (RTO) of near-zero in the event of an Availability Zone outage, without requiring manual intervention. Which storage configuration best meets these requirements?

  1. Amazon Elastic File System (Amazon EFS) using the Standard (Regional) storage class.Answer
  2. B
    Amazon S3 Glacier Flexible Retrieval using Standard retrieval options for failover storage.
  3. C
    A Pilot Light disaster recovery configuration in a secondary Region with pre-warmed, scaled-down EC2 instances and EBS volumes.
  4. D
    Amazon Elastic Block Store (Amazon EBS) volumes attached to Amazon RDS DB instances, leveraging RDS Read Replicas for automatic write failover.

Answer

Amazon Elastic File System (Amazon EFS) using the Standard (Regional) storage class.
The correct answer is Amazon Elastic File System (Amazon EFS) using the Standard (Regional) storage class. EFS natively replicates data across multiple Availability Zones in an AWS Region, provides concurrent shared access to EC2 instances, and automatically handles AZ failures to meet near-zero RTO and zero RPO requirements.

Step-by-Step Solution

1
Analyze the access pattern and durability requirements.
The application requires concurrent read/write access from EC2 instances in multiple Availability Zones, zero data loss (RPO=0RPO = 0), and durability of 99.999999999%99.999999999\%.
This filters out block storage (EBS) which cannot natively attach to multiple instances across AZs simultaneously.
2
Evaluate the recovery time requirements (RTO).
An AZ outage must be handled automatically without manual intervention, achieving a near-zero RTO.
This rules out S3 Glacier due to standard retrieval delays (3 to 5 hours) and Pilot Light disaster recovery configurations which require manual activation steps.
3
Assess the remaining storage configurations for multi-AZ failover capability.
Amazon EFS Regional storage class provides Multi-AZ durability, concurrent shared access, and native failover without manual intervention.
It meets both the high-availability metric (99.99%99.99\%) and the zero RPO/near-zero RTO targets.

Key Concept

Resilient and Highly Available Storage Infrastructure
Estimated Time:1m 30s
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Resilient and Highly Available Storage Infrastructure

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