Kubernetes / Rancher 2, mongo-replicaset with Local Storage Volume deployment
All this configuration is correct.
It's missing a detail since Rancher is a containerized deployment of kubernetes.Kubelets are deployed on each node in docker containers. They don't access to OS local folders.
It's needed to add a volume binding for the kubelets, like that K8s will be able to create the mongo pod with this same binding.
In rancher:Edit the cluster yaml (Cluster > Edit > Edit as Yaml)
Add the following entry under "services" node:
kubelet: extra_binds: - "/mongo:/mongo:rshared"