CSI inline ephemeral volumes

• Overview of CSI inline ephemeral volumes
  • Support limitations
• Embedding a CSI inline ephemeral volume in the Pod specification

Container Storage Interface (CSI) inline ephemeral volumes allow you to define a Pod spec that creates inline ephemeral volumes when a pod is deployed and delete them when a pod is destroyed.

This feature is only available with supported Container Storage Interface (CSI) drivers.

Overview of CSI inline ephemeral volumes

Traditionally, volumes that are backed by Container Storage Interface (CSI) drivers can only be used with a PersistentVolume and PersistentVolumeClaim object combination.

This feature allows you to specify CSI volumes directly in the Pod specification, rather than in a PersistentVolume object. Inline volumes are ephemeral and do not persist across pod restarts.

Support limitations

By default, OKD supports CSI inline ephemeral volumes with these limitations:

• Support is only available for CSI drivers. In-tree and FlexVolumes are not supported.

• OKD does not include any CSI drivers. Use the CSI drivers provided by community or storage vendors. Follow the installation instructions provided by the CSI driver.

• CSI drivers might not have implemented the inline volume functionality, including Ephemeral capacity. For details, see the CSI driver documentation.

Embedding a CSI inline ephemeral volume in the Pod specification

You can embed a CSI inline ephemeral volume in the Pod specification in OKD. At runtime, nested inline volumes follow the ephemeral lifecycle of their associated pods so that the CSI driver handles all phases of volume operations as pods are created and destroyed.

Procedure

1. Create the Pod object definition and save it to a file.

2. Embed the CSI inline ephemeral volume in the file.

   my-csi-app.yaml

   kind: Pod
   apiVersion: v1
   metadata:
     name: my-csi-app
   spec:
     containers:
       - name: my-frontend
         image: busybox
         volumeMounts:
         - mountPath: "/data"
           name: my-csi-inline-vol
         command: [ "sleep", "1000000" ]
     volumes: (1)
       - name: my-csi-inline-vol
         csi:
           driver: inline.storage.kubernetes.io
           volumeAttributes:
             foo: bar

   1	The name of the volume that is used by pods.

3. Create the object definition file that you saved in the previous step.

   $ oc create -f my-csi-app.yaml