I personally haven't used any such products in recent years, so I'm not in a position offer any specific suggestions. Another point to consider is that the DNS-321 formats HDDs using the Linux filesystem and I am not sure if that creates any dependencies that impacts how these types of utilities work. If the application is simply sweeping the HDD and writing to every sector it might not matter. If you want to play it safe, you can always mount the HDDs in a Windows PC, reformat, and then run the product locally from host PC.