We are using an external Docker EFS volume driver to setup shared storage for our containers.
We recently moved from Rancher 1.1.4 to 1.2.1 and now I find that the volume is mounted successfully when I create a new stack. However if I upgrade the stack (create another container on the same host) or delete and re-create the stack, then I see following exceptions in the rancher server logs.
2016-12-21 23:41:01,882 ERROR [:]    [ecutorService-8] [.e.s.i.ProcessInstanceDispatcherImpl] Unknown exception running process [instance.start:4594] on  java.lang.IllegalStateException: More than one volume exists for volume URI [efs:///var/lib/docker/volumes/efs/fromrancher_EFS] or name/externalId [fromrancher_EFS] and storage pool .
I can understand that since the volume is created per stack-it might be a problem if I delete and recreate that stack; though my assumption was that deleting the stack should also remove the persistent volume. But I don’t understand why Rancher would be creating 2 volumes if I upgrade the service.
Can someone please provide any pointers on using volumes with Rancher?