SOA-C02 Reliability and Business Continuity Practice Question
A company runs a critical application on Amazon EC2 instances across multiple Availability Zones. The application stores state data on a shared Amazon EFS file system. The SysOps administrator needs to ensure that the file system remains available if an entire Availability Zone fails. The file system must also provide low-latency access from all instances. Which configuration meets these requirements?
⚠ Common exam trap
It's easy for candidates to confuse EFS's Standard storage class with RDS's Multi-AZ deployment feature, or incorrectly assume that cross-Region replication is necessary for AZ-level fault tolerance, when in fact EFS's regional storage class already provides Multi-AZ redundancy within a single Region.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an EFS file system with the Standard storage class in the same Region, and mount it from all instances using the regional mount target.
The EFS Standard storage class stores data redundantly across multiple Availability Zones (AZs) within a Region, ensuring high availability and durability even if an entire AZ fails. By mounting the file system using the regional mount target (which resolves to the EFS file system's regional DNS name), instances in any AZ can access the file system with low latency, as EFS automatically routes traffic to the most appropriate mount target in the same AZ. This configuration meets both the availability and low-latency requirements without additional replication or failover complexity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create an EFS file system with the One Zone storage class and mount it from all instances.
Why it's wrong here
The One Zone storage class places file data in a single Availability Zone only, so if that AZ suffers an outage, the EFS file system becomes completely unavailable. This directly violates the requirement to remain available during an AZ failure, and it also risks permanent data loss if the AZ is destroyed. One Zone is intended for non-critical, reproducible workloads, not for critical applications requiring high availability.
- ✗
Create an EFS file system with the Standard storage class, enable replication to another Region, and use DNS failover.
Why it's wrong here
While enabling cross-Region replication provides disaster recovery across Regions, the stated requirement is to tolerate an Availability Zone failure within the same Region. A cross-Region replica would require DNS failover to a different Region, introducing significant cross-Region latency and a slower recovery time. It also adds unnecessary cost and complexity when the Standard storage class is already designed to replicate data across multiple AZs in the same Region.
- ✓
Create an EFS file system with the Standard storage class in the same Region, and mount it from all instances using the regional mount target.
Why this is correct
The Standard storage class automatically replicates file system data redundantly across multiple Availability Zones within the Region, providing built-in resilience against an AZ failure. The regional mount target is a single DNS name that resolves to mount targets in each AZ, so instances in any AZ can mount the same file system with low-latency access. If one AZ becomes unavailable, the DNS/ELF service continues to route instances to healthy mount targets, satisfying the high availability requirement.
- ✗
Create an EFS file system with the Standard storage class, and enable Multi-AZ deployment.
Why it's wrong here
Amazon EFS does not expose a configurable 'Multi-AZ deployment' option; instead, the Standard storage class inherently provides multi-AZ data replication across all Availability Zones in the Region. Enabling a non-existent setting is not possible and the premise is misleading. Any attempt to configure such an option would either fail or be redundant, providing no additional resilience beyond what Standard already delivers.
Visual reference
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.