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Amazon S3 vs Amazon EBS vs Amazon EFS Interview Questions and Answers

High-level interview guide comparing Amazon S3, Amazon EBS, and Amazon EFS with architecture diagrams, production use cases, best practices, and 15 interview questions.

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Amazon S3 vs Amazon EBS vs Amazon EFS Interview Questions and Answers

Cloud Interview Track

Storage Module — Lesson 03 of 08

Introduction

AWS provides multiple storage services designed for different workloads.

The three most commonly used services are:

  • Amazon S3 (Object Storage)
  • Amazon EBS (Block Storage)
  • Amazon EFS (File Storage)

Choosing the correct storage service is one of the most common cloud architecture interview topics.

AWS Storage Overview

flowchart LR

Application --> S3[Amazon S3]
Application --> EBS[Amazon EBS]
Application --> EFS[Amazon EFS]

What is Amazon S3?

Amazon S3 (Simple Storage Service) is an object storage service that stores files as objects inside buckets.

Best suited for:

  • Images
  • Videos
  • Documents
  • Static websites
  • Backups
  • Logs
  • Data lakes

S3 Architecture

flowchart LR

Application --> API[REST API]

API --> Bucket[S3 Bucket]

Bucket --> Object1
Bucket --> Object2
Bucket --> Object3

What is Amazon EBS?

Amazon Elastic Block Store provides persistent block storage volumes for EC2 instances.

It behaves like a hard disk attached to a virtual machine.

Best suited for:

  • Databases
  • EC2 Boot Volume
  • ERP Applications
  • Banking Systems

EBS Architecture

flowchart LR

EC2 --> EBS[EBS Volume]

EBS --> Snapshot

What is Amazon EFS?

Amazon Elastic File System is a fully managed shared file system.

Multiple EC2 instances can mount the same file system simultaneously.

Best suited for:

  • Shared folders
  • Web servers
  • CMS
  • Shared reports
  • Kubernetes

EFS Architecture

flowchart LR

EC2A --> EFS

EC2B --> EFS

EC2C --> EFS

Comparison

Feature S3 EBS EFS
Storage Type Object Block File
Access REST API Disk NFS
Shared Yes Limited Yes
Latency Moderate Very Low Low
Best For Files Databases Shared Storage
Scales Virtually Unlimited Volume Based Automatic
Mountable No Yes Yes

Production Architecture

flowchart TB

Users --> ALB

ALB --> EC2

EC2 --> EBS

EC2 --> EFS

EC2 --> S3

Which Service Should You Choose?

Requirement Service
Database EBS
EC2 Boot Disk EBS
Shared Files EFS
Images S3
Backups S3
Static Website S3
Kubernetes Shared Volume EFS
Application Logs S3

S3 Storage Classes

  • Standard
  • Intelligent Tiering
  • Standard IA
  • One Zone IA
  • Glacier Instant
  • Glacier Flexible
  • Glacier Deep Archive

EBS Volume Types

  • gp3
  • gp2
  • io2
  • io1
  • st1
  • sc1

EFS Performance Modes

  • General Purpose
  • Max I/O

Throughput Modes

  • Bursting
  • Provisioned
  • Elastic

Backup Strategy

flowchart LR

EBS --> Snapshot

EFS --> Backup

S3 --> Versioning

High Availability

Service High Availability
S3 Multi AZ
EBS Single AZ
EFS Multi AZ

Security

All three support

  • IAM
  • Encryption
  • CloudTrail
  • KMS
  • Backup
  • Monitoring

Interview Questions

1. What is the difference between Amazon S3, EBS and EFS?

Answer

S3 stores data as objects.

EBS stores data as disk blocks.

EFS stores data as files and directories.

2. Which storage is best for databases?

Answer

Amazon EBS because it provides low latency and high IOPS.

3. Which service supports multiple EC2 instances simultaneously?

Answer

Amazon EFS.

4. Which service is used for static website hosting?

Answer

Amazon S3.

5. Can Amazon S3 be mounted as a disk?

Answer

Not directly.

Applications normally access S3 through REST APIs or SDKs.

6. Can EBS be attached to multiple EC2 instances?

Answer

Normally no.

Some Multi-Attach volume types support specific clustered workloads.

7. Which storage provides the lowest latency?

Answer

Amazon EBS.

8. Which storage is cheapest for long-term backups?

Answer

Amazon S3 Glacier Deep Archive.

9. Which service automatically scales?

Answer

Amazon S3 and Amazon EFS.

10. Which service stores operating system files?

Answer

Amazon EBS.

11. What backup options are available?

Answer

  • S3 Versioning
  • EBS Snapshots
  • AWS Backup
  • EFS Backup

12. Which service is best for Kubernetes shared storage?

Answer

Amazon EFS.

13. When should S3 not be used?

Answer

S3 should not be used for:

  • Database files
  • Operating system disks
  • Low-latency transactional storage

14. Which AWS service is best for media storage?

Answer

Amazon S3 because it offers virtually unlimited scalability and integrates well with CloudFront, analytics, and lifecycle policies.

15. How do you choose between S3, EBS and EFS?

Answer

Use:

  • S3 for object storage, backups, logs, images, videos, and archives.
  • EBS for EC2 boot volumes, databases, and transactional workloads requiring low latency.
  • EFS for shared file systems, web servers, Kubernetes, and applications needing concurrent file access.

The choice should always be based on the application's access pattern, performance requirements, sharing needs, scalability, and cost.

Common Mistakes

  • Using S3 as a database disk
  • Using EBS for shared storage
  • Using EFS for high-performance databases
  • Forgetting EBS snapshots
  • Making S3 buckets public
  • Not enabling encryption
  • Ignoring lifecycle policies
  • Using expensive storage for archives

Best Practices

  • Use S3 for unstructured data.
  • Use EBS for databases.
  • Use EFS for shared storage.
  • Enable encryption everywhere.
  • Enable backups.
  • Use lifecycle policies.
  • Monitor storage usage.
  • Delete unused EBS volumes.
  • Enable S3 versioning.
  • Test restore procedures regularly.

Quick Revision

Service Best Use
Amazon S3 Images, Videos, Backups, Logs
Amazon EBS Databases, EC2 Boot Disk
Amazon EFS Shared Files, Kubernetes

Key Takeaways

  • Amazon S3 is object storage designed for massive scalability and durability.
  • Amazon EBS is block storage designed for low-latency, high-performance workloads.
  • Amazon EFS is a managed file system designed for shared access across multiple EC2 instances.
  • S3 is ideal for backups, media, static websites, and data lakes.
  • EBS is ideal for databases, operating systems, and transactional applications.
  • EFS is ideal for shared application data and container workloads.
  • Understanding when to use each storage service is a fundamental AWS architecture and interview skill.