Fast receive slow send on gigabit

[imported_latuszek]

I used iperf to test out my gigabit network and it seems from my computer to either of my two servers or to my media center pc, I get fast receiving, but not so fast sending.

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Server listening on TCP port 5001
TCP window size: 32.0 KByte
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Client connecting to 10.1.1.4, TCP port 5001
TCP window size: 32.0 KByte
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[1876] local 10.1.1.102 port 1418 connected with 10.1.1.4 port 5001
[ ID] Interval Transfer Bandwidth
[1876] 0.0-10.0 sec 822 MBytes 688 Mbits/sec
[1952] local 10.1.1.102 port 5001 connected with 10.1.1.4 port 1108
[ ID] Interval Transfer Bandwidth
[1952] 0.0-10.0 sec 471 MBytes 394 Mbits/sec

------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 32.0 KByte
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 10.1.1.3, TCP port 5001
TCP window size: 32.0 KByte
------------------------------------------------------------
[1876] local 10.1.1.102 port 1422 connected with 10.1.1.3 port 5001
[ ID] Interval Transfer Bandwidth
[1876] 0.0-10.0 sec 841 MBytes 704 Mbits/sec
[1848] local 10.1.1.102 port 5001 connected with 10.1.1.3 port 1051
[ ID] Interval Transfer Bandwidth
[1848] 0.0-10.0 sec 611 MBytes 512 Mbits/sec

How is this possible?? Shouldn't it be at least approx. the same speed each way? I tried setting up my computer as a server and then doing two clients at the same time, and this maxed out my computer's gigabit connection. But when I set up just 1 client (no matter how many threads, window size, etc) i seem to only get like 500 mbit/s

What other troubleshooting can I do. Also how come I can have like 700mbit speeds with iperf and only get like 250-300mbit/sec using window file sharing?? I am going from fast sata disk to a raptor??

Thanks for any help!