The GlusterFS package has been removed because it is no longer being maintained by Rancher or anyone in the community.
Rancher are working on “Project Longhorn” at the moment - which will provide new storage functionality: https://github.com/rancher/longhorn.
Your best option at the moment is to use NFS or look at some of the other storage providers like Portworx (https://portworx.com/) for this kind of thing. There are catalog entries for Portworx, and there is a Github repo with their free developer version here: https://github.com/portworx/px-dev.
So far, volume management has been one of my greatest sources of stress
with Docker. There are a bunch of cool-sounding volume management systems
available, including Portworx, Convoy, Flocker, etc. The problem I always
run into with the documentation is the assumption that either you’re
running your rancher instance on a non-RancherOS host, or you’re running it
on Amazon, etc. This makes getting anything set up and working an absolute
nightmare. I’m hoping that Longhorn will offer a reliable and easy to set
up storage option, but I’m not holding my breath.