CV0-004 Deployment Practice Question
A company is deploying a stateful application on AWS that requires a shared, POSIX-compliant file system that can be mounted on multiple Amazon EC2 instances simultaneously. The application also needs to support high throughput and must be durable across multiple Availability Zones. Which AWS storage service should the company use?
⚠ Common exam trap
The trap here is assuming that EBS Multi-Attach provides a shared file system, but it is block storage limited to a single AZ and requires a cluster file system.
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
✓
Amazon EFS
Amazon EFS is the correct choice because it provides a POSIX-compliant, shared file system that can be mounted on multiple EC2 instances across multiple Availability Zones. It offers high throughput and durability, making it ideal for stateful applications requiring shared storage. Other options either do not support POSIX semantics or do not span multiple AZs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Amazon FSx for Windows File Server
Why it's wrong here
Amazon FSx for Windows File Server provides a Windows-native file system with SMB protocol, not POSIX compliance. It is designed for Windows workloads and supports multi-AZ deployment, but it does not meet the POSIX requirement for Linux-based applications. While it offers shared storage, the protocol and semantics are not suitable for the stateful application described, which requires POSIX compliance.
- ✓
Amazon EFS
Why this is correct
Amazon EFS is a fully managed, POSIX-compliant file system that can be mounted on multiple EC2 instances simultaneously. It is durable across multiple Availability Zones and supports high throughput with Bursting or Provisioned Throughput modes. EFS is designed for shared access and automatically scales. This matches the requirements for a shared file system with multi-AZ durability and high throughput.
- ✗
Amazon EBS with Multi-Attach
Why it's wrong here
Amazon EBS Multi-Attach allows a single Provisioned IOPS volume to be attached to multiple EC2 instances in the same Availability Zone, but it does not provide a POSIX-compliant shared file system. It is block storage and requires a cluster-aware file system. It also does not span multiple Availability Zones. The requirement for a shared file system across AZs is not met by EBS Multi-Attach.
- ✗
Amazon S3
Why it's wrong here
Amazon S3 is an object storage service, not a POSIX-compliant file system. It can be accessed via REST API or mounted using third-party tools, but it does not provide native file system semantics like locking or concurrent write consistency. The application requires a shared file system that can be mounted on multiple instances, which S3 does not natively support. S3 is also not designed for low-latency file operations.
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 |
Go deeper
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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