The NetApp cinder driver defaults to raw format because the benefits of QCOW2 dont really apply when these images are hosted on a NetApp. NetApp can provide superior deduplication and compression when these settings are enabled on the FlexVol and additionally the deduplication happens across *all files in the volume not just within a cinder volume as with QCOW2. Another issue is that Qcow2 is not live migration safe on NFS when the cache=writeback setting is enabled (commonly used for performance improvement of qcow2). The customer may or may not need live migration though. If space savings are the desired outcome keep in mind that raw files are actually created as sparse files on the NetApp.