ClusterHQ Flocker is open source software that provides a framework for managing Docker containers and volumes. It allows users to move containerized applications and data across servers in a cluster.
Containerization isolates applications from each other while residing on a single storage node and sharing a single operating system. Flocker software uses the REST application programming interface (API) to manage volumes (the data associated with those containers) as ZFS file systems so that when a container is migrated to a new host, the volume moves with it. Without ClusterHQ Flocker software, moving containers and volumes must be done separately -- when a container is moved to a new host the volume does not follow. However, Flocker users also have the option to manage only volumes, while container management is performed separately through another service.
Flocker software is compatible with block-based storage backends, including Amazon Web Services Elastic Block Storage, Rackspace Cloud Block Storage, EMC ScaleIO, EMC XtremIO or systems that support the OpenStack Cinder API.