I have several swarm clusters at the moment without shared storage. I gathered some info about it and it seems that overall storage plugins for ceph and glusterfs volumes are not considered production ready. At the moment a good option from my point of view is to create glusterfs server from which volumes will be mounted to a common filesystem location (for example /storage) and every container will have a dedicated directory (for example /storage/container_1/volume_1).
Can you share your experiences in regard to shared storage for docker/swarm? Can you point any interesting howtos?