I've been trying to diagnose for a while why file transfers between my PC and my NAS are slow--often less than 1mbyte/sec over a wireless N network (or hell, even over a wired gigabit network). While doing various and sundry tests, I discovered something odd: no matter how I connected to my router, I could download from the Internet far faster than I could transfer files between machines on my local network, be it PC to PC, PC to NAS, or NAS to PC. In fact I could fully saturate my Internet downstream of 30 mbits/sec if I found a good site (Steam, for example).
I tried running iperf from several of my machines to my router (and vice versa; the router has DD-WRT installed), and came up with odd results: while directly connected to the router I could get the full gigabit bandwidth, but transfers from other PCs or the NAS were STILL below 1 MByte/s. Furthermore, while running iperf over wireless I got an average of 500 kbytes/sec bandwidth--and of course as soon as I stopped the iperf run and started an Internet download I could get six times that. Ditto when I tried testing over a powerline connection (though slightly faster in the file transfer department, about 750kbytes/sec).
I suck at networking and running iperf is the most complicated thing I've ever tried to do, so I'm out of ideas. What could be the cause of this oddball behavior? What other troubleshooting steps can I take? Why is networking such a god awful profession?