EFS - Elastic File System

EFS is a managed NFS (network file system) that can be mounted on many EC2 instances
EFS works with EC2 instances across multi AZs
EFS is highly available, scalable, but also more expensive (3x GP2) than EBS
EFS is pay per use
Use cases: content management, web service, data sharing, Wordpress
Uses NFSv4.1 protocol
We can use security groups to control access to EFS volumes
EFS is only compatible with Linux based AMIs (not Windows)

EFS Performance and Storage Classes

EFS Scale
- Thousands of concurrent NFS clients, 10 GB+ per second throughput
- It can grow to petabyte scale NFS automatically
Performance mode (can be set at EFS creation time)
- General purpose (default): recommended for latency-sensitive use cases: web server, CMS, etc.
- Max I/O - higher latency, throughput, highly parallel, recommended for big data, media processing
Storage tiers: lifecycle manage feature
- Standard: for frequently accessed files
- Infrequent access (EFS-IA): there is a cost to retrieve files, lower price per storage

EBS volumes
- Can be attached to only one instance at a time
- Are locked at the AZ level
- GP2: IO increases if the disk size increases
- IO1: can increase IO independently
- To migrate an EBS across AZ:
  - Take a snapshot
  - Restore the volume from the snapshot
- Root EBS volumes get terminated by default in the EC2 instance is terminated (this feature can be disabled)
EFS
- Can be mounted to multiple instances across AZs via EFS mount targets
- Available only for Linux instances
- EFS has a higher price point than EBS
- EFS is pay per second, we can leverage EFS-IA for cost saving