The Flocker plugin for Docker is a Docker volumes plugin connecting Docker on a host directly to Flocker, where Flocker agents will be running on the same host and hooked up to the Flocker control service.
You should not move a volume from one node to another unless you are sure no containers are using the volume on the source node.
The plugin will not stop volumes from being migrated out from underneath a running container. It is possible that Docker or your orchestration tool will prevent this from happening, but Flocker itself does not.
--volumes-from and equivalent Docker API calls will only work if both containers are on the same machine.
Some orchestration frameworks may not schedule containers in a way that respects this restriction, so check before using --volumes-from.
We recommend that when using the Flocker plugin for Docker that you only use named volumes (volumes which are specified using the -v name:/path syntax in docker run).
Anonymous volumes can be created if you use a Docker image that specifies volumes and don’t set a name for the volume, or if you add volumes in your Docker run commands without specified names (for example, -v /path).
Docker defines volume drivers for the entire container, not per-volume, so the anonymous volumes will also be created by Flocker.
As a result each time a container with an anonymous volume is started a new volume is created with a random name.
This can waste resources when the underlying volumes are provisioned from, for example, EBS.
A volume plugin makes use of the -v and --volume-driver flags on the docker run command.
The -v flag accepts a volume name and the --volume-driver flag a driver type.
The Flocker driver type is flocker.
docker run -ti -v volumename:/data --volume-driver=flocker busybox sh
In this example, a Flocker volume with name of volumename is created.
If a container is started with a volume of the same name in your Flocker cluster, the volume will be migrated to the calling node before Docker starts the container.
The Docker Remote API call which supports --volume-driver in the CLI is undocumented at time of writing.
However, currently is it is specified by the VolumeDriver attribute of HostConfig under POST /containers/create.
Set the container Mount attributes according to the instructions in the Docker CLI section.
More information about the VolumeDriver can be found in the Docker volumes plugin documentation.
To use Flocker Storage Profiles with the Flocker plugin for Docker you will need Docker 1.9 or later.
The Flocker plugin for Docker accepts a gold, silver or bronze profile by default, via the volume driver’s options parameter.
For example:
docker volume create --name <fastvol> -d flocker -o profile=gold docker run -v <fastvol>:/data redis
Note
Some backend providers may already have their own notion of profiles. Flocker Storage Profiles can be used to enable you to create volumes with those existing profiles.