When remove the default storage class annotation, leaving the cluster without a default storage class defined, we encounter different behavior:

1. with a PVC storage class, the PVC are kept
2. with a Snapshot storage class the VolumeSnapshot are deleted.

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1. in a cluster with PVC storage class change the annotation of the default storage class to "false"
2. observe the PVC are being kept
3. define a snapshot storage class (ocs-storagecluster-ceph-rbd-virtualization) as default by changing the annotation to "true"
4. observe the VolumeSnapshot are created
5. Remove the default storage class annotation and observe the VolumeSnapshot are Deleted 

PVC is kept while VolumeSnapshot is deleted

PVC and VolumeSnapshot should act in the same way. either both are deleted or both are kept