Your problem is not the software, it’s the USB. You’re clearly using either an old pc or an old disk drive with a USB 1.x connection, which is why you’re getting 10-12 Mbps. Figure out where the bottleneck is and stop blaming the software.
Data Hoarder
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
I'm not blaming the software! It's just what I have for now (a usb container). All I want is to use Android to perform the required operation.... So that I may not care about the time it takes.