- A
Amazon S3
Why wrong: Amazon S3 is an object storage service, not a file system. It cannot be directly mounted by EC2 instances as a POSIX-compliant file system shared across multiple instances.
- B
Amazon EBS
Why wrong: Amazon EBS provides block storage volumes. A standard EBS volume can be attached to only one EC2 instance at a time, and multi-attach EBS is limited to certain instance types and requires a clustered file system. Additionally, EBS does not automatically scale capacity.
- C
Amazon EFS
Amazon EFS provides a fully managed, scalable NFS file system that can be mounted by multiple EC2 instances across different Availability Zones. It automatically scales storage capacity on demand and charges only for the storage used, meeting all the stated requirements.
- D
Amazon FSx for Windows File Server
Why wrong: Amazon FSx for Windows File Server is a managed file system designed for Windows-based applications. The scenario specifies Linux instances, so Amazon EFS is the more appropriate and cost-effective choice.
CLF-C02 Cloud Technology and Services Practice Question
This CLF-C02 practice question tests your understanding of cloud technology and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is migrating a legacy on-premises application to AWS. The application requires a shared file system that can be mounted by multiple Amazon EC2 instances concurrently. The EC2 instances run Amazon Linux and are deployed across multiple Availability Zones for high availability. The file system must grow and shrink automatically as files are added or removed, and the company wants to avoid provisioning storage capacity in advance. Which AWS service should the company use to meet these requirements?
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 NFS file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones. It automatically scales storage capacity up and down as files are added or removed, eliminating the need to provision storage in advance. EFS supports the NFSv4.1 and NFSv4.0 protocols, making it ideal for shared file workloads on Amazon Linux.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Why it's wrong here
Amazon S3 is an object storage service, not a file system. It cannot be directly mounted by EC2 instances as a POSIX-compliant file system shared across multiple instances.
When this WOULD be correct
A company needs to store and retrieve any amount of data from anywhere (e.g., backup, static website hosting, or data lake) with high durability and scalability, and does not require a file system mount or concurrent file-level access from EC2 instances.
- ✗
Amazon EBS
Why it's wrong here
Amazon EBS provides block storage volumes. A standard EBS volume can be attached to only one EC2 instance at a time, and multi-attach EBS is limited to certain instance types and requires a clustered file system. Additionally, EBS does not automatically scale capacity.
When this WOULD be correct
A question requiring a single EC2 instance to have persistent, high-performance block storage for a database, with snapshots for backup and the ability to change volume type without stopping the instance (e.g., using EBS Multi-Attach for a limited number of instances in the same AZ).
- ✓
Amazon EFS
Why this is correct
Amazon EFS provides a fully managed, scalable NFS file system that can be mounted by multiple EC2 instances across different Availability Zones. It automatically scales storage capacity on demand and charges only for the storage used, meeting all the stated requirements.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon FSx for Windows File Server
Why it's wrong here
Amazon FSx for Windows File Server is a managed file system designed for Windows-based applications. The scenario specifies Linux instances, so Amazon EFS is the more appropriate and cost-effective choice.
When this WOULD be correct
A company needs a shared file system for Windows-based EC2 instances that supports SMB protocol, Active Directory integration, and requires high availability across multiple Availability Zones. The company is willing to provision storage capacity upfront and does not need automatic scaling.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓Amazon EFSCorrect answer▾
Why this is correct
Amazon EFS provides a fully managed, scalable NFS file system that can be mounted by multiple EC2 instances across different Availability Zones. It automatically scales storage capacity on demand and charges only for the storage used, meeting all the stated requirements.
✗Amazon S3Wrong answer — click to see why▾
Why this is wrong here
Amazon S3 is an object storage service, not a shared file system that can be mounted by multiple EC2 instances concurrently via a standard file system interface (POSIX). It does not support automatic file system mounting or concurrent read/write locking required for a shared file system.
★ When this WOULD be the correct answer
A company needs to store and retrieve any amount of data from anywhere (e.g., backup, static website hosting, or data lake) with high durability and scalability, and does not require a file system mount or concurrent file-level access from EC2 instances.
Why candidates choose this
Candidates may confuse S3's scalability and shared access capabilities with a file system, not realizing that S3 is object-based and lacks the file locking and POSIX compliance needed for concurrent mounting by EC2 instances.
✗Amazon EBSWrong answer — click to see why▾
Why this is wrong here
Amazon EBS volumes cannot be mounted by multiple EC2 instances concurrently; they are block-level storage attached to a single instance. The requirement for concurrent access across multiple instances and automatic scaling rules out EBS.
★ When this WOULD be the correct answer
A question requiring a single EC2 instance to have persistent, high-performance block storage for a database, with snapshots for backup and the ability to change volume type without stopping the instance (e.g., using EBS Multi-Attach for a limited number of instances in the same AZ).
Why candidates choose this
Candidates may confuse EBS with a shared file system because EBS volumes can be attached to one instance and then reattached to another, but they do not support concurrent multi-instance mounting.
✗Amazon FSx for Windows File ServerWrong answer — click to see why▾
Why this is wrong here
Amazon FSx for Windows File Server requires provisioning storage capacity in advance and does not automatically grow and shrink as files are added or removed. It also does not support Amazon Linux EC2 instances natively, as it is designed for Windows-based environments.
★ When this WOULD be the correct answer
A company needs a shared file system for Windows-based EC2 instances that supports SMB protocol, Active Directory integration, and requires high availability across multiple Availability Zones. The company is willing to provision storage capacity upfront and does not need automatic scaling.
Why candidates choose this
Candidates may confuse FSx for Windows File Server with a general-purpose shared file system, overlooking that it is Windows-specific and requires capacity provisioning, unlike EFS which is fully managed and elastic for Linux.
Analysis generated from the official CLF-C02blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Amazon EBS with a shared file system, overlooking that EBS volumes are single-instance attachments (except for the limited multi-attach feature) and require upfront capacity provisioning, whereas EFS is designed specifically for shared, elastic file storage across multiple instances and AZs.
Trap categories for this question
Scenario analysis trap
Amazon FSx for Windows File Server is a managed file system designed for Windows-based applications. The scenario specifies Linux instances, so Amazon EFS is the more appropriate and cost-effective choice.
Detailed technical explanation
How to think about this question
EFS uses a distributed data storage architecture where data is stored across multiple Availability Zones within a region, providing high durability and availability. Under the hood, EFS leverages the NFSv4.1 protocol with support for file locking and consistency semantics, and its performance modes (General Purpose and Max I/O) allow tuning for latency-sensitive or throughput-intensive workloads. A real-world scenario is a web application farm where multiple web servers share a common content repository; EFS automatically grows from gigabytes to petabytes without any capacity planning.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 |
What to study next
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Cloud Technology and Services — This question tests Cloud Technology and Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon EFS — Amazon EFS (Elastic File System) is a fully managed NFS file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones. It automatically scales storage capacity up and down as files are added or removed, eliminating the need to provision storage in advance. EFS supports the NFSv4.1 and NFSv4.0 protocols, making it ideal for shared file workloads on Amazon Linux.
What should I do if I get this CLF-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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