Assigning a dedicated disk to Docker

Is there a supported way to assign a dedicated disk to Docker similar to what is described for etcd? (https://gravitational.com/gravity/docs/requirements/#etcd-disk)

The reason behind it is to increase performance for Docker.

Yes there is a way, you can use host volume mounts check out application manifest, docs can be found here (https://gravitational.com/gravity/docs/pack/)