Thursday, July 3, 2008

Network card Speed and Duplex

We've been having a problem that's been plaguing us for weeks and today we finally solved it. We have 4 Windows Server 2003 machines running a handful of web sites in a cluster being accessed through a non-sticky VIP (Virtual IP). Some of the web sites allow uploading of files to the server which saves them to a NAS (Network Attached Storage) file share.

The problem was that two of the machines uploaded files like dogs and the other two were lightening fast. The speed difference was about 100 to 1.

The first test we ran was to make sure that it was the file share (NAS) that was the problem. We did this by setting up a test that uploaded files to each of the servers' local disks. They all ran fast. The same test was then modified to upload to the NAS file share via the servers and that isolated and confirmed the problem to be the NAS part of the equation.

It turned out that the problem was that the Speed & Duplex setting on the dog slow machines was marked as Auto. Changing this to 100 Mb Full solved this problem.

To get to this setting, on Windows Server 2003 click on Start -> right click My Computer and select Properties to open up the System Properties dialog. Select the Hardware tab and click on Device Manager to open the Device Manager window. Select the active network card and right click and bring up the properties dialog for that network adapter. On the properties dialog box for that adapter select the Advanced tab and in the Property list select Speed & Duplex and from the Value drop down select 100 Mb Full.

I hope this post helps at least just 1 person save several hours.

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