Volumes and persistent data

Containers are disposable, data is not

Anything written to the container filesystem dies with the container. A named volume is managed storage that outlives it, which is what makes running a database in a container reasonable.

Bind mounts map a host directory in and are the right tool for development, where you want your source to appear live inside the container. They are a poor fit for production, since they couple the container to the host layout.

A volume is not a backup. It is on one machine and it is one accidental prune away from being gone.