Docker Storage

Introduction

Docker has revolutionized the way applications are developed, deployed, and scaled. One of the critical components in the Docker ecosystem is Docker storage, allowing the persistence and sharing of data among containers.

Understanding Docker storage can seem complex, but this article aims to break down the concepts into digestible parts, showcasing examples and best practices.

What Is Docker Storage?

Docker storage refers to mechanisms that allow data to persist beyond the lifecycle of a container. This persistence ensures that important data remains accessible even if a container stops or fails.

Docker Storage Types

Docker provides different storage options to fit varying needs and use-cases.

1. Volumes

Volumes are the preferred mechanism for persisting data generated and used by Docker containers.

Example: Creating and Using a Volume

# Create a volume
docker volume create my_volume

# Run a container using the volume

docker run -v my_volume:/data ubuntu ls /data

2. Bind Mounts

Bind mounts allow mapping of a file or directory on the host machine to a container.

Example: Creating and Using a Bind Mount

# Run a container with a bind mount

docker run -v /host/path:/container/path ubuntu ls /container/path

3. tmpfs Mounts

These are stored in the host system's memory, suitable for storing sensitive information temporarily.

Example: Using a tmpfs Mount

# Run a container with a tmpfs mount

docker run --tmpfs /tmp ubuntu ls /tmp

Storage Drivers

Storage drivers allow Docker to manage container images and writeable container layers. Some popular storage drivers include:

Overlay2: Default for many distributions and recommended by Docker.

aufs: Used in older versions, still supported.

btrfs: Known for its high performance and reliability.

Example: Checking the Storage Driver

# Check the current storage driver

docker info | grep "Storage Driver"

Docker Compose and Volumes

Docker Compose is a tool to define and run multi-container applications. You can define volumes in a docker-compose.yml file.

Example: Docker Compose with Volumes

version: '3'
services:
  web:
    image: nginx
    volumes:
      - my_volume:/usr/share/nginx/html
volumes:
  my_volume:

Storage Best Practices

• Use Volumes for Persistent Data: Volumes are Docker-managed and survive container restarts.
   
• Avoid Sensitive Data in tmpfs: While convenient for temporary data, it's in-memory and can be lost.
   
• Choose the Right Storage Driver: Understanding the storage needs of your application can guide the choice of the driver.

Also see, Ensemble Learning