The csi-ceph module is designed to integrate DKP with Ceph clusters and provides storage management based on RBD (RADOS Block Device) or CephFS. It allows creating StorageClasses in Kubernetes using the CephStorageClass resource.

For more details about the module, refer to the module documentation section.

Module architecture

The following simplifications are made in the diagram:

  • The diagram shows containers in different pods interacting directly with each other. In reality, they communicate via the corresponding Kubernetes Services (internal load balancers). Service names are omitted if they are obvious from the diagram context. Otherwise, the Service name is shown above the arrow.
  • Pods may run multiple replicas. However, each pod is shown as a single replica in the diagram.

The Level 2 C4 architecture of the csi-ceph module and its interactions with other components of Deckhouse Kubernetes Platform (DKP) are shown in the following diagram:

csi-ceph module architecture

Module components

The module consists of the following components:

  1. Controller: A controller that reconciles the following custom resources:

    CephStorageClass specifies the storage class type (CephFS or RBD), reclaim policy, Ceph cluster connection parameters, and additional parameters specific to each storage class type. Depending on the storage class type, these parameters are used by the provisioner of either the rbd.csi.ceph.com or cephfs.csi.ceph.com CSI driver when managing volumes.

    The CephMetadataBackup custom resource is used in migration and recovery workflows implemented by module hooks, rather than by the main runtime controller.

    It consists of the following containers:

    • controller: Main container.
    • webhooks: A sidecar container that implements a webhook server for StorageClass resources validation.

  2. CSI driver (rbd/cephfs): An implementation of the CSI driver for the rbd.csi.ceph.com or cephfs.csi.ceph.com provisioner. The CSI driver is selected by setting the storage class type in the CephStorageClass custom resource.

    The csi-cephfs CSI driver follows the standard CSI driver architecture used in DKP.

    The csi-rbd CSI driver uses an architecture that differs from the standard CSI driver architecture.

Module interactions

The module interacts with the following components:

  • Kube-apiserver:

    • Watches PersistentVolume, PersistentVolumeClaim, VolumeAttachment, and StorageClass resources.
    • Reconciles CephClusterConnection and CephStorageClass custom resources.
    • Creates StorageClass resources.

The following external components interact with the module:

  • Kube-apiserver: Validates StorageClass resources.

Additional resources