Volume vs tmpfs in Docker: Key Differences and Usage

In Docker, volumes store data persistently on disk and can be shared between containers, while tmpfs mounts store data temporarily in memory and are erased when the container stops. Use volumes for durable storage and tmpfs for fast, ephemeral data.

Quick Comparison

This table summarizes the main differences between Docker volumes and tmpfs mounts.

Factor	Volume	tmpfs
Storage Location	Disk (persistent storage)	Memory (RAM, ephemeral)
Data Persistence	Data persists after container stops	Data lost when container stops
Sharing	Can be shared between multiple containers	Limited to single container
Performance	Slower due to disk I/O	Faster due to in-memory storage
Use Case	Persistent data like databases, logs	Temporary data like caches, session data
Size Limit	Limited by disk space	Limited by available RAM

Key Differences

Volumes in Docker are designed for persistent data storage. They store data on the host disk and keep it safe even if the container is removed or restarted. Volumes can be shared across multiple containers, making them ideal for databases, logs, or any data you want to keep long-term.

On the other hand, tmpfs mounts store data in the host's memory (RAM). This makes them very fast but temporary. When the container stops or restarts, all data in a tmpfs mount is lost. They are useful for temporary files, caches, or sensitive data that should not be written to disk.

Because tmpfs uses RAM, it is limited by available memory and should be used carefully to avoid exhausting system resources. Volumes do not have this limitation but are slower due to disk access.

Code Comparison

Here is how you mount a volume in Docker to persist data in a container.

bash

docker run -d \
  --name my_container \
  -v my_volume:/app/data \
  busybox sleep 3600

Output

Container started with a volume named 'my_volume' mounted at /app/data inside the container.

tmpfs Equivalent

This example shows how to mount a tmpfs in Docker for fast, temporary storage inside a container.

bash

docker run -d \
  --name my_tmpfs_container \
  --tmpfs /app/cache \
  busybox sleep 3600

Output

Container started with a tmpfs mount at /app/cache storing data in memory.

When to Use Which

Choose volumes when you need data to persist beyond the container's life or to share data between containers. This is common for databases, logs, or configuration files.

Choose tmpfs when you need fast, temporary storage that disappears when the container stops. This is ideal for caches, session data, or sensitive information that should not be saved to disk.

Key Takeaways

Use Docker volumes for persistent, shareable data stored on disk.

Use tmpfs mounts for fast, temporary data stored in memory.

Volumes keep data after container stops; tmpfs data is lost.

tmpfs is limited by RAM size; volumes depend on disk space.

Choose tmpfs for caches and sensitive ephemeral data.