I am having trouble getting my Gigabit network to work properly between my desktop computer and my Windows Home Server. When copying files to my server (connected through my switch), I am seeing file transfer speeds of below 10MB/s, sometimes even below 1MB/s.

The machine configurations are:

Desktop

• Intel Core 2 Quad Q6600
• Windows 7 Ultimate x64
• 2x WD Green 1TB drives in striped RAID
• 4GB RAM
• AB9 QuadGT motherboard
• Realtek RTL8810SC network adapter

Windows Home Server

• AMD Athlon 64 X2
• 4GB RAM
• 6x WD Green 1,5TB drives in storage pool
• Gigabyte GA-MA78GM-S2H motherboard
• Realtek 8111C network adapter

Switch

dLink Green DGS-1008D 8-port

Both machines report being connected at 1Gbps. The switch lights up with green lights for those two ports, indicating 1Gbps.

When connecting the machines through the switch, I am seeing insanely low speeds from WHS to the desktop measured with iperf: 10Kbits/sec (WHS is running iperf -c, desktop is iperf -s). Using iperf the other way (WHS is iperf -s, desktop iperf -c) speeds are also bad (~20Mbits/sec).

Connecting the machines directly with a patch cable, I see much higher speeds when connecting from desktop to WHS (~300 Mbits/sec), but still around 10Kbits/sec when connecting from WHS to the desktop. File transfer speeds are also much quicker (both directions).

Log from desktop for iperf connection from WHS (through switch):

C:\temp>iperf -s
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 8.00 KByte (default)
------------------------------------------------------------
[248] local 192.168.1.32 port 5001 connected with 192.168.1.20 port 3227
[ ID] Interval       Transfer     Bandwidth
[248]  0.0-18.5 sec  24.0 KBytes  10.6 Kbits/sec

Log from desktop for iperf connection to WHS (through switch):

C:\temp>iperf -c 192.168.1.20
------------------------------------------------------------
Client connecting to 192.168.1.20, TCP port 5001
TCP window size: 8.00 KByte (default)
------------------------------------------------------------
[148] local 192.168.1.32 port 57012 connected with 192.168.1.20 port 5001
[ ID] Interval       Transfer     Bandwidth
[148]  0.0-10.3 sec  28.5 MBytes  23.3 Mbits/sec

What is going on here?

Unfortunately I don't have any other gigabit-capable devices to try with.