Is anyone using RMAN with DDBoost for RMAN to backup Oracle sitting on XtremIO to Data Domain?

We have just tested a restore of a test Oracle DB ( which is backed up using RMAN) back to an XtremIO array from the Data Domain.

The DB is approx 7TB  in size. On the XtremIO it used approx 4.2TB of capacity. When we done a full restore back to the same LUNs on the array we used up almost an additional TB of capacity on the array.

I would have expected the restored data to have been deduped on ingest by the XtremIO and there to have been very little if any additional space used up. This does not seem to be the case.

Has anyone else seen this and if so is this to be expected when using Data Domain?

Any assistance would be gratefully appreciate.

Thanks

D