What is EFS, and when would you use it over EBS or S3?
AWS · Intermediate level
Answer
EFS is managed elastic NFS shared storage mountable by multiple compute nodes across AZs. I use it when applications need shared POSIX file access; EBS is block storage and S3 is object storage.
Technical explanation
EFS security combines mount targets, security groups, POSIX permissions, access points, IAM, and encryption.
AWS storage choices are based on access model: block storage for disks, object storage for objects, shared file storage for POSIX file access, and ephemeral storage for rebuildable temporary data.
Performance must be evaluated at both the storage layer and instance/network layer; a high-performance volume cannot exceed instance bandwidth limits.
Backups are only useful when restore is tested, retention is aligned to policy, and encryption/cross-account/cross-Region protection is considered.
Hands-on example
1. Provision the storage option in a test environment with encryption, tags, backups, and monitoring enabled.
2. Run a workload-specific benchmark for IOPS, throughput, latency, concurrency, or shared-file behavior.
3. Create and restore a backup or snapshot to prove recovery rather than only creation.
4. Document the selected storage type, limits, cost assumptions, and restore runbook.
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