Configuring a custom backend

Available since MOSK 24.3 TechPreview

MOSK enables its clients to define their own volume backends for the MOSK Block Storage service (OpenStack Cinder) through the spec:features:cinder:volume:backends structure in the OpenStackDeployment custom resource:

spec:
  features:
    cinder:
      volume:
        backends:
          <UNIQUE_BACKEND_NAME>:
            enabled: true
            type: statefulset
            create_volume_type: true
            values:
              conf:
              images:
              labels:
              pod:

The enabled and create_volume_type parameters are optional. With create_volume_type set to true (default), the new backend will be added to the Cinder bootstrap job. Once this job is completed, the volume type for the custom backend will be created in OpenStack.

The supported value for type is statefulset.

The list of keys you can override in the values.yaml file of the Cinder chart includes conf, images, labels, and pod.

When you define the custom backend for the Block Storage service, MOSK deploys individual pods for it. These pods have separate Secrets for configuration files and ConfigMaps for scripts.

Example of configuration of a custom volume backend for Cinder:

The configuration example deploys an additional StatefulSet for the Cinder volume backend using the NFS driver, running a single replica on nodes labeled kubernetes.io/hostname:service-node. Privilege escalation for the Cinder volume and backup pods is driver-specific and may not be required.

spec:
  features:
    cinder:
      volume:
        backends:
          nfs-volume:
            type: statefulset
            values:
              conf:
                cinder:
                  DEFAULT:
                    cluster: ""
                    enabled_backends: volumes-extra-nfs
                  volumes-extra-nfs:
                    nas_host: 1.2.3.4
                    nas_share_path: /cinder_volume
                    nas_secure_file_operations: false
                    nfs_mount_point_base: /tmp/mountpoints
                    nfs_snapshot_support: true
                    volume_backend_name: volumes-extra-nfs
                    volume_driver: cinder.volume.drivers.nfs.NfsDriver
              pod:
                replicas:
                  volume: 1
                security_context:
                  cinder_volume:
                    container:
                      cinder_volume:
                        privileged: true
              labels:
                volume:
                  node_selector_key: kubernetes.io/hostname
                  node_selector_value: service-node

  services:
    block-storage:
      cinder:
        values:
          conf:
            enable_iscsi: true
          pod:
            security_context:
              cinder_backup:
                container:
                  cinder_backup:
                    privileged: true

See also

OpenStack official documentation: Volume drivers