I'm studying about Docker and I couldn't understand very well the difference between what storage drivers are used for and what volume drivers are used for. My theory (please correct me if I'm wrong) is the storage drivers manage the way Docker deals underneath with the writable layer, can use overlay, overlay2, aufs, zfs, btrfs and so on. Volume drivers, however, deal with volumes underneath, like it can be a local volume (in this case I think it will use a storage driver) or can be a remote one (like EBS). Am I right?
What are the differences between the concepts of storage driver and volume driver in Docker?
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2 Answers
Docker uses storage drivers to store image layers, and to store data in the writable layer of a container. Docker uses Volume drivers for write-intensive data, data that must persist beyond the container’s lifespan, and data that must be shared between containers. So, I understand Storage Drivers are used with image and container layers while Volume Drivers are used for persistent container application data. See the first three paragraphs of this Docker documentation: https://docs.docker.com/storage/storagedriver/
Docker engine volume enable engine deployments to be integrated with external storage systems such as Amazon EBS, and enable data volumes to persist beyond the lifetime of a single Docker host. Here the term 'local' in concept of Docker volume driver means the volumes esdata1 and esdata2 are created on the same Docker host where you run your container. By using other Volume plugins, e.g.,-driver=flocker. You are able to create a volume on a external host and mount it to the local host, say, /data-path.
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