Why cloning a VM disk from CephFS to block PVC is creating empty device?

Issue

• Used a DataVolume to clone a VM disk from cephFS to Ceph RBD storage class.

apiVersion: cdi.kubevirt.io/v1beta1
kind: DataVolume
metadata:
  name: mydisk-clone
spec:
  source:
    pvc:
      name: "mydisk"
      storageClassName: ocs-external-storagecluster-cephfs
      namespace: vm-cnv
  storage:
    resources:
      requests:
        storage: 33Gi
    storageClassName: ocs-external-storagecluster-ceph-rbd

• But there is nothing in the cloned volume and it's all zeroes.

sh-5.1$ dd if=/dev/disk-poised-goat bs=1M  |hexdump -C
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
33792+0 records in
33792+0 records out
35433480192 bytes (35 GB, 33 GiB) copied, 66.1271 s, 536 MB/s
840000000