Getting Started with Amazon EFS: Scalable, Shared Storage for Your EC2 Instances

When building applications on AWS, one common challenge developers face is sharing files across multiple EC2 instances in a reliable, scalable, and secure way.

This is where Amazon Elastic File System (EFS) comes in.

EFS provides:

Shared storage — mount the same file system across hundreds of EC2s Highly available — data replicated across multiple Availability Zones (AZs) Elastic scaling — grows and shrinks automatically with your data Pay-as-you-go — no need for capacity planning

In this blog, let’s set up a production-ready EFS and mount it on two EC2 instances across different AZs.

Step 1: Create an Amazon EFS File System

1. Open the EFS Console → Click Create file system.
2. Configure settings:

• Name: my-efs-demo (optional).
• VPC: Choose your default or custom VPC.
• File system type:
• Regional → Recommended for HA (replicates data across AZs).
• One Zone → Cheaper but riskier (single AZ only).
• Backups: Enable automatic backups (recommended for production).
• Lifecycle management: Move old files to IA (30 days) or Archive (90 days).
• Encryption: Enable (default AES-256 or AWS KMS).
• Throughput mode:
• Elastic (recommended): Scales IO automatically, pay-per-use.
• Provisioned: Fixed throughput for predictable workloads.
• Performance mode:
• General Purpose (recommended): Low latency.
• Max I/O: High throughput, slightly higher latency.

Click Next → Create

Your EFS file system is now ready.

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Step 2: Configure Network Access

For EC2 instances to connect to EFS, we need mount targets and the right security groups.

1. In EFS Network settings, select:

• VPC → Same as your EC2s.
• Subnets → Pick at least two subnets in different AZs (for Regional).

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1. Create a Security Group (e.g., EFS-SG-Demo) and allow:

• Inbound Rule: NFS (port 2049) from your EC2 Security Group.

Tip: Always keep EC2 and EFS security groups linked properly; otherwise, your mounts will fail.

Save and attach the security group.

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Step 3: Launch EC2 Instances with EFS

Now let’s spin up two EC2 instances in different AZs and mount our shared EFS.

1. Launch Instance A in us-east-1a (or any AZ).

• Attach the same VPC.
• Select EFS-SG-Demo.
• In Storage settings → File Systems, add the EFS you just created.

1. Launch Instance B in another subnet (e.g., us-east-1b).

• Attach the same security group as Instance A.
• Add the same EFS mount.

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Step 4: Test File Sharing

Now, let’s test whether files written in one instance appear in the other.

On Instance A:

sudo su
echo "hello world" > /mnt/efs/fs1/hello.txt
cat /mnt/efs/fs1/hello.txt

Output:

hello world

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On Instance B:

ls /mnt/efs/fs1
cat /mnt/efs/fs1/hello.txt

Output:

hello.txt
hello world

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Why Use Amazon EFS in Production?

• Web applications — Store shared assets, images, logs
• CI/CD pipelines — Share build artifacts across runners
• Analytics workloads — Multiple compute nodes reading the same dataset
• Machine learning — Shared training data across GPUs

With EFS + EC2, you don’t worry about provisioning storage, scaling, or data consistency — AWS takes care of it.

Notes:-

Amazon EFS makes it easy to:

• Build scalable, highly available applications
• Share storage seamlessly across EC2s
• Keep costs under control with pay-as-you-go

If you’re running multi-instance workloads or want a serverless-friendly file system, EFS is one of the best choices on AWS.

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