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Windows 2008 network performance problem

Today I was facing weird problem at our customer. They have IBM HS21 blade server with build-in dual-port Broadcom network card. There was only Windows 2008 installed with all up2date drivers. Everything worked fine besides network performance. Upload from server to other servers was around 20MBps, which is fine. Problem was download to server, because it was 1-2MBps.

We have tried all network scenarios but we couldn’t find problem on network. Then we tried to boot BartPE CD and copied data. It was 20MBps upload and download. Then we boot Kubuntu Live CD and also network was alright. So problem was not at network and neither in hardware. Problem was in operating system and its settings.

After some time I remembered that I already solved such a problem couple months ago. Problem was in implementation of TCP Offload and TCP Chimney features in Windows operating systems. I disabled all three features (TCP Chimney Offload, Receive Side Scaling and Network Direct Memory Access) as mentioned at this KB article. After disabling this features upload and download on same Windows operating system was 20MBps.

I think these features should be disabled by default and enabled if people want to and not other way around.

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