Storage
Amazon EFS
Shared, elastic NFS file storage
Amazon EFS is a managed NFS file system that scales elastically and is accessible from multiple AZs. Mount targets in each AZ let many instances share the same file system concurrently.
When to use it
- Web serving and content management shared across a multi-AZ fleet
- Lift-and-shift apps expecting POSIX file semantics
- Any workload needing concurrent shared file access across AZs
When NOT to use it
- Single-instance high-IOPS databases (use EBS io2)
- Object storage use cases (use S3)
- Windows-only SMB requirements (use FSx for Windows)
Key exam points
- Multi-AZ by design — the standard answer for 'shared file storage across an Auto Scaling group'
- Regional service; mount targets per AZ
- Infrequent Access storage classes reduce cost for rarely accessed files
- POSIX permissions and NFS protocol — not a block or object store
Compared with
- Amazon EBS — EBS is single-AZ single-instance block storage; EFS is multi-AZ shared file storage.
- Amazon S3 — S3 is object storage with HTTP access; EFS is a mounted file system.