i have the same problem, originally i was using VCB exporting to tape, now with VDP the only possible option is to backup the VDP appliance somehow. i was told some folks have come up with interesting workarounds in the various backup solutions on the market.
just be sure to test your backups once you have a solution figured out since VDP is so closely tied to vcenter and sso - well at least it appears that way to me. please correct me if i'm wrong.
dhayashi