Transferring data

So my setup is a little unusual at the moment. 

I have two wifi connections. One for my internet, and another router is only hooked to my NAS without internet. I have a reason for this, my NAS connection is only temporary until I get it fully setup and then move it to my workshop. 

My question is, I have an external HDD with about 1TB of data that I would like to move to my NAS. The only way I know how to make a transfer is with the external connected to my computer, and then my computer connected to my NAS. But this is a large transfer and would not allow me to use my computer with the internet.  So Is there a work around?

Can I plug my external into my NAS and start a transfer without my computer being necessary? Ive tried this, but once I switch connections on my computer the transfer stops. And ideas? I would really appreciate it! Thank you!

EDIT: My transfer speed is about 10MB/s over wifi and only about 3MB/s connected directly to the NAS. So either way its going to take a long time. So I can’t just leave my computer without being able to use it for that long of a period. 


Unfortunately, even when a USB device is connected to a WD My Book Live Duo, an active host computer system is required in order to handle file management operations.