Choosing a Shared NFS File System for EC2 Instances Across Availability Zones
A company is migrating a legacy on-premises application to AWS. The application requires a shared file system that supports the NFS protocol and must be accessible from multiple EC2 instances across different Availability Zones. The file system must provide high durability and low latency. The company also needs to control access to the file system using IAM policies. The solutions architect needs to choose the appropriate AWS storage service. Which service should the architect use?
Quick Answer
The answer is Amazon EFS with IAM authorization. This is the correct choice because Amazon EFS provides a fully managed, shared NFS file system that is inherently accessible from multiple EC2 instances across different Availability Zones, offering the high durability and low latency required for the migration. EFS also uniquely supports IAM policies for fine-grained access control, allowing you to manage permissions at the file system level without needing separate authentication mechanisms. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this question tests your ability to distinguish between shared file services and block or object storage; the common trap is selecting EBS, which is zone-scoped and single-instance, or FSx for Lustre, which is optimized for HPC rather than general NFS workloads. Remember the memory tip: “EFS is Elastic File Sharing” — it spans AZs and honors IAM, while EBS is bound to a single zone and instance.
⚠ Common exam trap
SAP-C02 often tests the difference between EFS and FSx for Lustre. Candidates might choose FSx for Lustre for high performance, but overlook the requirement for NFS and IAM authorization, which EFS provides.
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 with IAM authorization.
Amazon EFS is a fully managed, scalable, elastic NFS file system for Linux-based workloads. It supports the NFS protocol and can be mounted on multiple EC2 instances across different Availability Zones simultaneously. EFS provides high durability (11 9's) and low latency. Additionally, EFS supports IAM authorization for controlling access to the file system, allowing fine-grained permissions. Therefore, Amazon EFS with IAM authorization meets all requirements.
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 S3 with S3 File Gateway to present as a file system.
Why it's wrong here
S3 File Gateway presents S3 objects over NFS, but it caches on-premises or on EC2 and does not deliver the low-latency shared file system with native IAM file-level authorisation required across Availability Zones. It suits hybrid access to S3 data, not a multi-AZ shared NFS workload.
- ✗
Amazon EBS with a Provisioned IOPS volume type, mounted on multiple instances using a cluster file system.
Why it's wrong here
EBS volumes attach to a single EC2 instance in one Availability Zone; a cluster file system layered on top does not provide the multi-AZ NFS access or IAM-based file system authorisation the scenario demands. It is tempting for low-latency block storage on one instance, where Provisioned IOPS would be the right fit.
- ✓
Amazon EFS with IAM authorization.
Why this is correct
Amazon EFS provides a shared, Multi-AZ NFS file system with high durability and low latency, satisfying the cross-AZ access requirement. Enabling IAM authorization lets you enforce access control through IAM policies, meeting the stated security constraint. FSx for Windows uses SMB, and EBS cannot be shared across Availability Zones.
- ✗
Amazon FSx for Lustre with a persistent deployment type.
Why it's wrong here
FSx for Lustre is a high-performance parallel file system for HPC and machine learning workloads, and its persistent deployment type does not provide the multi-AZ durability the stem requires. Amazon EFS offers NFS across Availability Zones with IAM-based file system policies. Lustre would suit scratch processing or compute-intensive analytics.
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
Related to this question
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Same concept, more angles
1 more way this is tested on SAP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a legacy on-premises application to AWS. The application requires a shared file system that can be mounted by multiple EC2 instances concurrently, with strong consistency and low-latency access. Which AWS storage solution should be used?
hard- A.AWS Storage Gateway File Gateway
- ✓ B.Amazon EFS
- C.Amazon EBS with multi-attach enabled
- D.Amazon S3
Why B: Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be mounted concurrently by multiple EC2 instances across multiple Availability Zones. It offers strong read-after-write consistency and low-latency access, making it ideal for shared file workloads requiring POSIX permissions and concurrent access.
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 Amazon Web Services exam blueprint
This SAP-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 SAP-C02 exam.