CLF-C02 Cloud Technology and Services Practice Question
A company runs a web application on multiple EC2 instances across multiple Availability Zones. All instances need to access and share the same file system simultaneously to read and write shared configuration files. Which AWS storage service supports simultaneous access from multiple EC2 instances?
⚠ Common exam trap
Many candidates confuse Amazon EBS with a shared file system, not realizing that standard EBS volumes are single-instance attachable, while EFS is purpose-built for multi-instance shared 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 is a fully managed, NFS-based file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones, providing shared access for reading and writing configuration files. It uses the NFSv4.1 protocol and supports thousands of simultaneous connections, making it ideal for shared storage scenarios.
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
An EBS volume can only be attached to a single EC2 instance at a time (except for EBS Multi-Attach, which is limited to specific volume types and use cases). It is not designed for simultaneous shared access across multiple instances.
- ✗
Instance Store
Why it's wrong here
Instance Store volumes are physically attached to the host server of a single EC2 instance, providing very high I/O performance but with critical limitations. They are ephemeral: data persists only for the life of the instance and is lost on stop, hibernate, or termination, making them unsuitable for durable shared storage. Because they are local to one host, they cannot be mounted by multiple EC2 instances simultaneously, so they fail the shared-file-system requirement.
- ✓
Amazon EFS
Why this is correct
Amazon EFS is a fully managed, POSIX-compliant network file system built on NFSv4 that can be mounted concurrently by hundreds of EC2 instances across multiple Availability Zones. It scales storage capacity and throughput automatically as files are added or removed, eliminating capacity provisioning. With features like VPC mount targets, security groups, and IAM authorization, EFS provides a native shared file system that supports consistent, low-latency reads and writes from many instances, exactly matching the scenario.
- ✗
Amazon S3
Why it's wrong here
S3 can be used to share files but is accessed via API calls, not mounted as a native file system. For applications that require a mounted file system interface with shared access, EFS is the correct service.
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
About these practice questions
This CLF-C02 question is part of Courseiva's 993-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.