Docker Storage

There are two basic storage concepts in Docker.

• Storage Drivers
• Volume Drivers

Docker Volumes

Docker stores data in /var/lib/docker

# Docker folder structure
/var/lib/doocker
  aufs
  condainers
  image
  volumes  

Volume Mounting

Here we create a Docker volume and mount it into a container

# Create a Docker volume.
# Note: if you mount a volume that does not exist Docker will auto-create it for you.
docker volume create data_volume

# This creates a folder in
# /var/lib/docker/volumes/data_volume

# Mounting the volume in Docker
docker run -v data_volume:/var/lib/mysql mysql

Bind Mounting

We can also use a directory on the host instead of a Docker volume. This directory could be another mounted volume.

docker run -v /data/mysql:/var/lib/mysql mysql

New Way of Mounting Volumes

The -v parameter is the old way of mounting volumes. The --mount parameter is now the preferred way of doing it.

docker run \
  --mount type=bind,source=/data/mysql,target=/var/lib/mysql \
  mysql

Storage Drivers

Docker uses storage drivers to enable all of the volume features such as layering, copy on write, etc. Some supported storage drivers are:

• AUFS
• ZFS
• BTRFS
• Device Mapper
• Overlay
• Overlay2

Volume Drivers

• local: Used by Docker to create volumes in /var/lib/docker/volumes/
• Azure File Storage
• Convoy
• Digital Ocean Block Storage
• Flocker
• gce-docker
• GluserFS
• NetApp
• RexRay
• Portworx
• VMware vSphere Storage
• ….

Choosing a volume driver during runtime.

# This uses rexray to provision a driver in AWS EBS
docker run -it \
  --volume-driver rexray/ebs \
  --mount src=ebs-vol,target=/var/lib/mysql
  mysql