Amazon EFS (Elastic File System) is a fully managed, serverless, elastic NFS (Network File System) shared file storage service that automatically scales from gigabytes to petabytes as you add or remove files. Unlike EBS which attaches to a single instance, EFS can be simultaneously mounted by thousands of EC2 instances across multiple Availability Zones.

Amazon EFS is designed to provide shared file storage for Linux-based workloads in AWS. It implements the NFSv4 protocol, which means any EC2 instance (or on-premises server via Direct Connect or VPN) can mount the file system and access the same files concurrently. EFS is truly elastic — it grows and shrinks automatically as files are added and removed, and you only pay for the storage you actually use. There is no need to pre-provision a size like you do with EBS.

Key Characteristics of Amazon EFS

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Shared access — thousands of EC2 instances across multiple AZs can mount and access the same EFS file system simultaneously
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Fully managed — AWS handles provisioning, patching, replication, and scaling automatically
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Elastic and serverless — capacity scales automatically up and down with no pre-provisioning required
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Pay-per-use — billed only for the storage actually used, no minimum commitment
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POSIX-compliant — supports standard Linux file system semantics, permissions, and ownership
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High availability — data is stored redundantly across multiple Availability Zones in a region
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High durability — 99.999999999% (11 nines) durability
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Supports NFSv4.0 and NFSv4.1 protocols
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Linux only — EFS does NOT support Windows EC2 instances (use Amazon FSx for Windows File Server instead)

Common Use Cases for Amazon EFS

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Content management systems — shared web content served by multiple web server instances behind a load balancer
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Media processing workflows — multiple instances reading and writing to the same media files
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Home directories — centralized user home directories accessible from any instance
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Data science and analytics — shared training datasets accessed by multiple compute nodes simultaneously
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Container storage — persistent shared storage for containerized applications in ECS or EKS
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DevOps and CI/CD — shared build artifacts and source code accessible across build agents
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Lift-and-shift applications — migrating on-premises NFS workloads to AWS without refactoring