Ref: https://learn.cantrill.io/courses/docker-fundamentals/lectures/44151338 =OR= https://www.youtube.com/watch?v=OAeVsjwRVe8

• Summary:
• Contents:

Writable Layer

• 🔧 Container data changes during runtime are stored by default in this layer
  • other storage options need extra configuration
• Requires a file system driver
  • Has overhead
  • Impacts performance (while container is running)
• Linked to container's lifecycle → does not persist when container is deleted
  • stopping container keeps the layer and eliminates performance hit
• Union File System overlays files and directories from separate file systems
  • End result: a “single” file system
  • Data tightly coupled with the host → data cannot be easily moved
• Summary diagram

Temporary File System (tmpfs or tempfs)

• 🔧 One tmpfs volume can be mounted per container
  • Can't be shared between containers
  • Uses host memory → very fast
  • Ephemeral (not persistent)
• Useful for temporary or sensitive files of short usage that shouldn't be stored in disk

Bind Mounts

• 🔧 Map external directory to a container directory
  • External directory can be in the host machine or even remote
• Persistent
  • Persist after container deletion
  • Can be moved between containers
• One container can have multiple bind mounts
• Multiple containers can access the same bind mount/external directory
  • ‼️ No file locking → extra IO/RW management to make sure data doesn't get corrupted!