So, I've come across a 2x10Gb/s nic on ebay for next to nothing. It has SFP (not SFP+ btw) connectors but of course I need RJ45 ethernet to connect my PC. Cat6 would be able to carry the frequency needed to deliver that speed, but I'm wondering about the SFP connector. I guess something like this would be sufficient if I just wanted to get 1Gb/s, but how do I go from SFP to RJ45 at 10Gb/s? The adapter only says 1Gb, and I guess one could not force it to work with higher speeds? Any ideas?
SFP can't do 10G ethernet, only SFP+ can.
The fastest you can do is 4.25Gb using SX multimode Fibre (Fibre Channel) or 1Gbit with twisted copper (aka regular ethernet)
However, have a look at Infiniband. Providing you don't want super long cable runs, it can be pretty cheap.