Understanding CSI architecture and communication

General Discussions
4

Things are slowly starting to fall into place, although it’s unfortunate I don’t speak Japanese!

Sorry, I describe your questions as much as I can in English :sweat:

and the “node” part responds to attach/detach requests (from the kubelet).

To be exact, “controller” part responds to attach/detach requests too(from GitHub - kubernetes-csi/external-attacher: Sidecar container that watches Kubernetes VolumeAttachment objects and triggers ControllerPublish/Unpublish against a CSI endpoint).
The main role of “node” part is reponding to mount/umount request(from kubelet).
(mount/umount request = Node(Un)stageVolume/Node(Un)publishVolume)

I wonder then what would be the correct way to write something like csi-driver-host-path but which works across multiple nodes. At volume creation time, it needs to choose a node to create the volume on (unless the PVC requested a specific node);

Kubernetes CSI supports the Topology feature.

If you want to select a node, you need to use the Topology feature.

I don’t know much local-zfs-provisioner, but maybe GitHub - topolvm/topolvm: Capacity-aware CSI plugin for Kubernetes is closed to you want to know.

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The whole reason I started down this path is because local-zfs-provisioner doesn’t support volume resize operations, and in turn this is because it uses sig-storage-lib-external-provisioner which doesn’t support resize.

CSI Driver can inform what feature was supported using the capability to sidecar apps and kubelet(also whether support a resize feature).

And an application that requests to a resizes request to CSI Driver is GitHub - kubernetes-csi/external-resizer: Sidecar container that watches Kubernetes PersistentVolumeClaims objects and triggers controller side expansion operation against a CSI endpoint.
Maybe sig-storage-lib-external-provisioner is a library that only executes provisioning a volume(create/delete a volume).
sig-storage-lib-external-provisioner is being used from an external-provisioner.

It’s not that I need this functionality - it’s more that I want to understand how this all hangs together, and storage provisioning in k8s in general. So thank you for helping my understanding :slight_smile:

:smiley_cat:

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