EFS

In this lesson we cover file-system storage on AWS, focusing on Amazon Elastic File System (EFS). EFS is a managed, NFS-based file system (commonly NFS v4.1) that lets multiple Linux-based compute instances mount the same file system concurrently. Because EFS uses NFS, it is not supported on Windows EC2 instances.

A presentation slide about AWS Elastic File System (EFS) and FSx showing the NFSv4 protocol, with a Linux icon and a crossed-out Windows icon to indicate compatibility, plus illustrations of compute and scalability.

EFS is deployed inside an Amazon VPC. To make a file system accessible, EFS creates mount targets in the subnets you select. Each mount target receives its own IP address within its subnet — instances use those IPs to reach and mount the file system. For high availability, create mount targets in multiple Availability Zones (AZs) so EC2 instances in each AZ can mount a local mount target and avoid cross‑AZ network hops.

A network diagram titled "How EFS Works" showing an EFS filesystem inside a VPC with mount targets in two Availability Zones. Each mount target (10.0.1.10 and 10.0.2.10) is connected to a compute instance.

Storage classes EFS provides multi‑AZ and single‑AZ storage options to balance durability and cost. Use the table below to compare the storage classes and pick the right one for your workload.

Storage Class	Resilience	Typical use cases
`EFS Standard`	Multi-AZ (high durability and availability)	Shared file systems for production workloads, content management, web servers
`EFS Standard - Infrequent Access (Standard‑IA)`	Multi-AZ with lower cost for infrequently accessed files	Cost-optimized for infrequently accessed data while retaining multi‑AZ resilience
`EFS One Zone`	Single AZ (lower cost)	Non-critical or AZ-specific workloads where cross-AZ redundancy is not required
`EFS One Zone - Infrequent Access (One Zone‑IA)`	Single AZ with lower cost for infrequent access	Cost-sensitive, single-AZ use cases with infrequent access patterns

A presentation slide titled "Elastic File System (EFS)" showing two colored boxes comparing "Standard Storage Classes" and "One Zone Storage Classes." Each box lists the corresponding EFS options (EFS Standard / Standard‑IA vs EFS One Zone / One Zone‑IA) with brief notes about multi‑AZ resilience and cost savings.

Performance and throughput modes EFS separates performance behavior (latency, IOPS characteristics) from throughput allocation. Choose the appropriate mode for your workload. Performance modes

Performance Mode	Best for	Notes
General Purpose (default)	Latency-sensitive workloads: web servers, CMS, home directories, general file serving	Low latency for most file operations
Max I/O	Scale-out workloads with high aggregate throughput and many concurrent operations	Slightly higher per-operation latency but higher aggregate throughput and IOPS

Throughput modes

Throughput Mode	How it works	When to use
Bursting Throughput (default)	Throughput scales with stored data; supports bursts above baseline	Cost-effective for most workloads with variable needs
Provisioned Throughput	You specify throughput independent of stored data size	Use when you need sustained higher throughput than bursting mode can provide

A slide titled "Elastic File System (EFS)" highlighting the General Purpose Performance Mode. It lists latency-sensitive use cases like web-serving, content-management systems, home directories, and general file serving.

Mounting EFS on an EC2 Linux instance Follow these steps to mount an EFS file system from a Linux EC2 instance. Replace fs-01234567 with your EFS File System ID and us-east-1 with your region where applicable.

Install the EFS mount helper (amazon-efs-utils). Use your distribution’s package manager:

# Amazon Linux / RHEL / CentOS
sudo dnf -y install amazon-efs-utils
# or on older systems:
sudo yum -y install amazon-efs-utils

# Debian / Ubuntu (may require extra repository configuration on some releases)
sudo apt-get update
sudo apt-get install -y amazon-efs-utils

Create a mount point and mount the file system:

# create a local directory to mount to
sudo mkdir -p /mnt/efs

# Recommended: use the EFS mount helper (simpler and supports TLS)
sudo mount -t efs fs-01234567:/ /mnt/efs

# To enable encrypted-in-transit (TLS) if supported by the mount helper:
sudo mount -t efs -o tls fs-01234567:/ /mnt/efs

# Fallback: mount directly with the NFS client (use if amazon-efs-utils is unavailable)
sudo mount -t nfs4 -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2 fs-01234567.efs.us-east-1.amazonaws.com:/ /mnt/efs

Optional: persist the mount with /etc/fstab. Example fstab entry using the mount helper and TLS:

fs-01234567:/ /mnt/efs efs defaults,_netdev,tls 0 0

Important network and security considerations

Ensure the mount targets and EC2 instances are in the same VPC (or connected via VPC peering / Transit Gateway where supported).
Security groups and NACLs must allow NFS traffic — typically TCP port 2049 — between the instances and the mount targets.
For cross-AZ reliability, create mount targets in each AZ you use.

Make sure your security groups and network ACLs permit TCP port 2049 (NFS) between your instances and the EFS mount targets. If network rules block NFS, mounts will fail. Also confirm that route tables and subnet configuration allow connectivity to the mount target IPs.

EFS mounts are NFS-based and supported only on Linux clients. EFS is not a bootable (root) volume — you cannot install an OS on EFS. Use EBS for root volumes and booting instances. Consider EFS Access Points and POSIX permissions for per-application access control.

Summary

Amazon EFS is a managed, NFS-based file system service that enables concurrent, shared access from multiple Linux instances.
EFS file systems are exposed inside a VPC using mount targets; each mount target is an IP address in a chosen subnet/AZ.
Choose between Standard (multi‑AZ) and One Zone storage classes depending on durability and cost requirements.
Select the appropriate performance mode (General Purpose or Max I/O) and throughput mode (Bursting or Provisioned) to match application latency and throughput needs.
EFS cannot be used as a boot/root volume — use block storage (EBS) for booting.

Links and references

Introduction

Services - Networking

Services - Storage

Services - Compute

Services - Database

Services - Application Integration

Services - Data and ML

Services - Migration and Transfer

Services - Management and Governance

Services - Security

Bringing it all together

Designing for Security

Designing for Reliability

Designing for Performance

Designing for Cost-Optimization

Applying your Design Skills

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