CLF-C02 Cloud Technology and Services Practice Question
Which AWS storage service is designed for shared file storage accessible simultaneously by multiple EC2 instances using the NFS protocol?
⚠ Common exam trap
A common mix-up: candidates confuse EBS (block storage) with a shared file system, not realizing that EBS volumes are single-instance attached by default, while EFS is purpose-built for multi-instance NFS access.
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 (Elastic File System) is a fully managed, scalable NFS file system that can be mounted concurrently on multiple EC2 instances. It uses the NFSv4.1 protocol, enabling shared access across Availability Zones and instances, which is exactly what the question describes.
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 EBS
Why it's wrong here
Amazon EBS provides block-level storage volumes that attach to a single EC2 instance at a time, regardless of instance or volume type. Even though EBS Multi-Attach exists for io1/io2 volumes, it only supports up to 16 instances within the same Availability Zone and lacks the cross-AZ, NFS-based shared file system semantics that a shared file store requires. Furthermore, EBS is raw block storage that requires a file system to be applied, but that file system is not natively accessible by multiple instances with proper file locking and POSIX semantics. Therefore, EBS cannot serve as the shared, mountable NFS file system for multiple EC2 instances across multiple AZs.
- ✗
Amazon S3
Why it's wrong here
Amazon S3 is an object storage service that provides a RESTful HTTP API for storing and retrieving objects, not a POSIX file system interface that can be mounted by EC2 instances. While you can integrate S3 with applications via SDKs or mount it indirectly using third-party tools or AWS Storage Gateway, it does not natively support concurrent multi-mount access as an NFS file system. S3 offers eventual consistency (now strong but not file semantics), but it lacks file-level locking, file attributes, and hierarchical directory semantics expected from a shared network file system. Therefore, S3 cannot serve as a direct replacement for a shared file storage solution for Linux instances needing NFS.
- ✓
Amazon EFS
Why this is correct
Amazon EFS is a fully managed, elastic NFS file system designed to be mounted on multiple EC2 instances simultaneously, whether they reside in the same or different Availability Zones. It supports NFSv4.1 and NFSv4.0, providing a standard file system interface with automatic scaling from gigabytes to petabytes as you add or remove files. With EFS, applications get consistent performance and a shared, POSIX-compliant file system that enables concurrent access from hundreds of Linux instances, making it the ideal choice for shared workloads. Because EFS automatically replicates data within and across AZs, it also provides high availability and durability.
- ✗
Amazon FSx for Windows File Server
Why it's wrong here
Amazon FSx for Windows File Server delivers fully managed Windows-native file shares using the Server Message Block (SMB) protocol, integrated with Active Directory and Windows-specific features like NTFS permissions and shadow copies. While it can be accessed from Linux instances using the SMB client, it is not an NFS-based file system and is optimized for Windows workloads, not for Linux applications expecting NFS semantics. The question explicitly requires an NFS file system for shared use across EC2 instances, so FSx for Windows would introduce protocol mismatch and require non-standard client configuration. Therefore, it is not the correct choice for a shared file system for Linux instances.
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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CLF-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 CLF-C02 exam.