I now hooked up my external HDD via USB and it can write data 10-20 times faster. so the HDD is not the bottleneck.
So, how come via network I only get 12 Mbit? It jsut goes from my desktop to the router (6ft patch cable) and via router USB to the external HDD. It all should be at least 100 Mbit hardware. so withoverhead I should get much more than just 12 Mbit
I don't think I was able to accidentally limit the speed.