Extremely slow transfer speeds over ethernet

I have to say, I'm NOT a fan of these type of Combo UNITS.  I have no experiance with the Virgin Media Superhub.  I've ran into issues with Motorola's Cable Modem with built in Wifi someone at work got, and I told him not to, and he had slow Wifi to his devices.  A problem fixed once he returned that and got a seperate Cable Modem and Wifi Router.

Is that your issue?  I will say my OLD ReadyNAS NV+ V2 with a ARM CPU was sslllllooowww over my Gigabit Network.  I wired up my house with Cat6 cable a few years ago.  It all ends up at my 24 port Gigabit Switch.   My new ReadyNAS 516 with a much faster Intel CPU, Network speeds are 4-5 times faster.  I can basically max out that Gigabit speed transfering large files.  Where as I would see around 20 or so MB/s on my old NAS, I'm in the 90-100+ MB/s with this newer NAS.  That's what Windows is showing me transfering to/from it.  When I got the new NAS I did get a new Managed 24-port Switch so I could bond the 2 Ethernet ports on the NAS. That shouldn't have any effect on a single large file transer though.

200kB/s is really BAD  Do you have any issues with the HDD?  One going bad?  Lots of errors on a transfer?  It could be a bad Switch with your so called Superhub!   You may want to try a differnt switch to plug your devices in and see if you can get better speed that way.  Maybe it's a cable or connector issue.  It's a trial and error type thing unless you have access to costly testing equepment.   You should be getting around 20MB/s.  

Let me time how long it takes to to transfer a 6GB file from my NAS to my Windows 10 PC.   Well it'll take a while to find a file around 6 GB, so I'm timing one that's just over 9GB in size.  It took 1:35.87.  Or about 1 minute and 36 seconds!!!  For a file that is 3GB larger in size.  But again I'm doing 90-100+MB/s.  You should still be getting around that 20MB/s.   Hopefully you can figure this out.  All anyone can else can do is guess.  Has it always been this slow or did it happen a few weeks or months ago?  Or you just happen to notice the speed and why it was taking so long to do things?    What kind of speed are you getting going from your NAS to your Computer and back again?  Is it the same as doing rsync?

So again, you have to narrow down issues it could be.  NAS? Switch? Cables?  etc.  Something is clearly wrong.   3.5 hours and still going is crazy long.  It shouldn't take more then say 5 minutes for you to transfer that 1 6GB file.