maybe a little bit offtopic but:
if you want to use deduplication i would recommend you to turn off the compression of UrBackup.
We achieve between 60 and 67% dedupe Rate with VHD files but just ~17% with VHDZ. (Depending on how much time he gets to dedupe while IDLEing and the VHD - File ratio) [Use Dedupe in Hyper-V Infrastructure Mode - because VHD files]
Also VHD is much faster.