I'm generally not doing any copying to or from the drives on my desktop, the server shares are mapped and I treat them like local drives. That's why I want throughput to be optimal right from the server, maxing out the gigabit ethernet. I run things like VM's stored directly on the server. My primary benchmark is CrystalDiskMark which doesn't use the desktop drives, it's just testing the drive I select (which is one of the mapped drives of the server shares). All that really should be happening in any usage scenario is that whatever I'm loading from the server is only being loaded into RAM - local drives are irrelevant.
Can you try and compare iperf -c on a Windows machine vs on a *nix VM on the same machine (imitate my situation)? I doubt my slower iperf on Windows is an isolated case. I tried iperf on a Windows 7 VM on the same host as the Ubuntu VM, and the Windows 7 VM performs just as poorly as the host Windows 7. The Ubuntu VM still beats either Windows 7 when doing iperf -c.
Can you try and compare iperf -c on a Windows machine vs on a *nix VM on the same machine (imitate my situation)? I doubt my slower iperf on Windows is an isolated case. I tried iperf on a Windows 7 VM on the same host as the Ubuntu VM, and the Windows 7 VM performs just as poorly as the host Windows 7. The Ubuntu VM still beats either Windows 7 when doing iperf -c.