How to map persistent volumes in Openshift 4 to Ceph RBD images in OCS 4

• The ocs-storagecluster-ceph-rbd storage class will be used by an OCP application deployment to create RWO (ReadWriteOnce) persistent storage.

• The persistent storage will be a Ceph RBD (RADOS Block Device) volume (object) in the Ceph pool ocs-storagecluster-cephblockpool.

• Many-a-times during the investigation of an issue, it may be required to map a persistent volume to the backing Ceph RBD image.

• Run the following command to get a list of Pod Name, PV Name, Storage Class and Volume Handle.

    $ oc get pv -o 'custom-columns=NAME:.spec.claimRef.name,PVNAME:.metadata.name,STORAGECLASS:.spec.storageClassName,VOLUMEHANDLE:.spec.csi.volumeHandle'
  

• In the output of the above command, the second half of the Volume Handle column matches what your RBD image is named inside of Ceph, with csi-vol- appended to the front.

• To get the full name of the RBD image in one command, run the following :

    $ oc get pv <PV_NAME> -o jsonpath='{.spec.csi.volumeHandle}' | cut -d '-' -f 6- | awk '{print "csi-vol-"$1}'
  
    Replace <PV_NAME> with the persistent volume name.