Ref: https://learn.cantrill.io/courses/1820301/lectures/41301664

• Summary:
• Contents:

Amazon EFS (Elastic File System) - Architecture

• 🔧 EFS = AWS implementation of NFSv4
  • 💡 NW File System (NFS) is a fairly common storage standard for shared files
  • Provides NW-based FSs which can be mounted within 1+ Linux EC2 instance(s)
    • Allows storing media outside of EC2 instances → 👍 stateless instances
    • Shared → One FS can be used by multiple Linux instances at once
  • Private service, FS is accessed via mount targets inside VPC subnets
    • Can be accessed via hybrid NWing from on-premises: VPC peering, VPN or DX
    • To ensure HA in a region, put mount targets in multiple AZs (same as with NATGWs)

• Files in EFS exist separately from EC2 instances
  • 💡 Just like EBS volumes exist separately from EC2
    • EFS is file storage and EBS is block storage
  • Data is not lost if instances are deleted and recreated
    • This makes EC2 instances stateless, which is usually desired
• ‼️ EFS is ONLY for Linux instances!!
  • 💡 In exam, if you're looking for a FS for EC2 Windows instances, you probably want to choose FSx for Windows File Server instead
• Linux uses a tree structure for its FS
  • Devices can be mounted into directories/folders in the hierarchy
  • A FS could e.g. be mounted into a directory called /nfs/media
• ❗ FSs use POSIX permissions
  • 💡 POSIX = a standard for interoperability which is used in Linux
    • A POSIX permissions FS can be understood by any Linux distribution
    • Additional info: https://en.wikipedia.org/wiki/File_system_permissions

EFS Additional Settings/Characteristics

• Creating a FS in EFS involves providing several settings

EFS Performance Settings

• Throughput modes:
  1. Bursting (Default)
     • Has a burst pool, but throughput scales with FS size
       • 💡 Akin to GP2 volumes in EBS
         • The more data you store in the FS, the better performance you get
  2. Enhanced
     1. Elastic
        • Throughput scales automatically, only pay for what you use
        • For workloads with unpredictable I/O
     2. Provisioned
        • Throughput requirements can be specified separately from FS size
          • 💡 Akin to IO1 volumes in EBS
        • More flexible, but not used by default
  • Throughput Modes - UI Screenshot
• Performance modes:
  1. General Purpose (Default)
     • Ideal for latency-sensitive use cases, web servers, Content Management Systems (CMSs), home directories, or even general file serving
  2. Max I/O
     • Scales to higher levels of aggregate throughput and IOPS…
       • …with trade-off of increased latency
     • Ideal for highly parallel apps
       • e.g. big data media processing, scientific analysis…
• Ref (extra info and numbers): https://docs.aws.amazon.com/efs/latest/ug/performance.html
  • 💡 No need to remember raw numbers for exam

EFS Storage Settings

• Storage classes:
  1. Standard (Default)
     • For frequently accessed files
  2. Infrequent Access (IA)
     • For infrequently accessed files
     • Cheaper than Standard
  3. Archive
     • Very infrequently accessed files
     • Cheaper than IA
  • 💡 Similar to S3 storage classes (similar trade-offs)