flocker seems to be dead (or rather clusterHQ seems to be dead).
It’s also worth looking at the https://kubernetes.iokubernetes.io/docs/concepts/storage/volumes as the next version of rancher will be heavily based on k8s
PS - sorry about the fugly links, I guess I don’t even enough street cred to post more than 1 link atm
If you don’t need much IO, you can try NFS, but if you do, NFS is definitely not the solution, I mean, you can’t mount volumes from NFS directly to containers, you maybe have to sync NFS directory to another directory, then mount this one on your container.
I noticed a thread here about Rook.io It seems to simplify setting up Ceph within a Kubernetes cluster; which would probably go very well with Rancher 2.0; or 1.6.x if you are using kubernetes with it.