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📁 Elastic File System (EFS)
Overview

📁 Elastic File System (EFS)

Gerald Koh Gerald Koh
March 25, 2026
3 min read
AWS EFS Storage

What is EFS?

Amazon Elastic File System (EFS) is AWS’s managed file storage service that provides shared, elastic file storage for multiple compute instances.

It is a managed Network File System (NFS) that can be mounted by multiple clients at the same time.

  • EFS uses the NFSv4 protocol.
  • Multiple EC2 instances can access the same EFS file system concurrently.
  • EFS is commonly used when multiple instances need shared access to the same files.
  • EFS is designed to scale automatically as your file system grows.
Note

Think of EFS as shared file storage for EC2, whereas EBS is typically attached to one instance at a time.

Compatibility

EFS can be mounted from supported EC2 clients using NFS.

  • Supported for Linux-based EC2 instances.
  • Supported for EC2 macOS instances.
  • ❌ Not supported for Windows–based EC2 instances.
Important

If an exam question asks for a shared file system for Windows EC2 instances, EFS is not the right answer.

File system types

EFS offers two file system types.

Types

  • Regional: stores data across multiple Availability Zones within the same Region and is the recommended option for higher availability.
  • One Zone: stores data in a single Availability Zone and is lower cost, but less resilient than Regional.
Note

Use Regional when you want multi-AZ resilience. Use One Zone only when lower cost matters more than multi-AZ durability.

Storage classes and lifecycle management

EFS supports lifecycle management to move files between storage classes automatically based on access patterns.

Storage classes

  • EFS Standard: for frequently accessed files and the lowest latency.
  • EFS Infrequent Access (IA): for files accessed only occasionally.
  • EFS Archive: for very infrequently accessed files.

Key points

  • Lifecycle management can automatically move files from Standard to IA and then to Archive.
  • By default, AWS’s recommended lifecycle policy transitions files to IA after 30 days and to Archive after 90 days without access.
  • Files can also be configured to move back to Standard on first access.
Tip

A good way to remember this: Standard for active data, IA for cold data, Archive for very cold data.

Performance modes

AWS Console screenshot of EFS performance and throughput mode options

EFS provides two performance modes.

Types

  • General Purpose (Default & Recommended): best for latency-sensitive workloads such as web servers, CMS workloads, and general file serving.
  • Max I/O: designed for highly parallel workloads that can tolerate higher latency.

Key points

  • AWS recommends General Purpose for most workloads.
  • Max I/O is considered a previous-generation option.
  • The performance mode is set at creation time and cannot be changed later.
  • Max I/O is not supported for One Zone file systems or file systems using Elastic throughput.
Important

For most exam scenarios, choose General Purpose unless the question clearly describes a highly parallel workload that can tolerate higher latency.

Throughput modes

Throughput mode determines how much throughput the file system can deliver.

Types

  • Elastic (Default & Recommended): throughput scales automatically up or down with workload demand.
  • Provisioned: you specify the throughput you want, independent of storage size. Useful when you need predictable throughput regardless of file system size.
  • Bursting: throughput scales with the amount of data stored in EFS Standard.