Not necessarily. You could use --net=host and -v /db_data:/db_data (equivalent of `sudo mount --bind /db_data /the/containers/root/fs/dir/db_data`)

Run like this, there is no disk or network performance difference between running the db process directly on the host or via a Docker container.

As others have mentioned, this is a really poor article.

Volume mounts inside containers bypass unionfs. There isn't anything inherently different about using a partition from container or from a host.