AWS EFS vs S3: When and How to Use Each

After learning EC2, EBS, and Load Balancers, the next big challenge is handling files like images, uploads, and static content. At first, it might seem like everything can be stored on the server itself, but in real systems that approach quickly breaks.

This is where AWS provides two powerful solutions: EFS (Elastic File System) and S3 (Simple Storage Service).

The Problem: Multiple Servers, One Data Source

User → Load Balancer → web-01
                     → web-02

If a user uploads a file to one server, another server may not have that file. This creates inconsistency in a load-balanced setup.

Multiple servers require shared storage or centralized storage.

Solution 1: Using EFS (Shared File System)

EFS allows multiple EC2 instances to access the same file system at the same time. It behaves like a shared disk that is mounted on each server.

EC2-1 ─┐
       ├── EFS (shared folder)
EC2-2 ─┘

How EFS Works (Steps)

Create EFS file system
Attach security group (NFS port 2049)
Install EFS client on EC2
Mount EFS to a directory
Use it like a shared folder

mount -t efs fs-xxxx:/ /mnt/efs

Once mounted, all EC2 instances see the same files.

Where EFS is Used

Shared uploads
WordPress media storage
Legacy applications

Limitations of EFS

More expensive
Slower than local disk
Requires mounting

          EFS is useful when your application requires a traditional file
          system.
        

Solution 2: Using S3 (Object Storage)

S3 works completely differently. Instead of mounting storage, files are accessed using URLs.

https://my-bucket.s3.amazonaws.com/image.jpg

Applications upload files to S3 and then access them directly via HTTP.

How S3 Works (Steps)

Create a bucket
Upload files
Set permissions (optional public access)
Access files via URL

Where S3 is Used

Images and media
Static website hosting
Backups and logs
Large-scale storage

S3 is the modern and most scalable way to handle files.

EFS vs S3 (Key Differences)

EFS → File system (mounted)
S3  → Object storage (URL-based)

EFS is used inside EC2
S3 is accessed over the internet
EFS is shared storage
S3 is global storage

Real Architecture Comparison

Using EFS

User → ALB → EC2 → EFS

Using S3 (Modern)

User → S3 (direct)
User → EC2 (logic only)

Best Practice Architecture

User
 ↓
ALB
 ↓
EC2 (application)
 ↓
S3 (images/files)

In modern systems, EC2 handles logic, while S3 handles file storage.

When to Use What

Use EFS → when app needs shared file system
Use S3 → for images, videos, and static content

What I Learned

Not all storage is the same in cloud
EFS solves shared filesystem problems
S3 solves scalability and performance issues
Modern apps prefer S3 over EFS

Good architecture separates compute (EC2) from storage (S3).

Final Thoughts

This lesson helped me understand one of the most important decisions in cloud architecture: how to store and serve data efficiently. Choosing between EFS and S3 is not just a technical choice — it directly impacts performance, cost, and scalability.

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