slow performance of Microsoft 2003 server attached to 3750 at Gig

Unanswered Question
Jun 7th, 2007

We have been seeing slow performance issues with Microsoft 2003 server and file shares when both are set to gigabit (both the switch and server show 1000 full), but when set slow speed 100 full server performnce is much better.

I have this problem too.
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Anand S Thu, 06/07/2007 - 10:25

Hi Jeff,

can u make the gigabit port manually as Full Duplex? i think that would make sense, bcoz i was facing the same kind of situation with the Intel Gigabit NIC, when i made manually as Full Duplex, it worked out fine. i.e 1000Mbps Full Duplex manually.

Jeff.sadowski Thu, 06/07/2007 - 12:04

The Cisco 3750-24E switches do not have a manual full duplex option. When setting the switch port to Gigabit, it returns a message that it will only by full duplex. When I look at the port status, it shows the port as being 1000 Full. This is being contacted to HP server running Windows 2003.

jedavis Thu, 06/07/2007 - 13:57

In the Gigabit Ethernet world, it makes no sense to hard code speed and duplex values. Autonegotiation is mandatory for GigE. Platforms that allow you to hard-code the speed and duplex are simply limiting the connection parameters that are advertised and accepted during that autonegotiation.

In general, I think the whole fear of autonegotiation is outdated, based upon the incompatibilities that existed in the early years after its introduction. I had some network admins at one site that insisted on setting the speed and duplex on workstations and switch ports claiming that it just didn't work. Then I ran some port error reports for them comparing their site to others that used autonegotiation and demonstrated that they had 10 times higher error rates than the next worst location due to duplex mismatches.

Sorry - got off on a rant. My point is that I would just let it autonegotiate. Here's an interesting article from Sun...

Jeff.sadowski Tue, 06/12/2007 - 07:29

We have not had 100% success rate using autonegotiate for switch to server interfaces. We do use it for general PC workstation for end user, because of the admin required to set speed and duplex for our company. On the server side of the house, we have had many times that a duplex mismatch has happened. Setting switch or server to autonegotiate is not full proof solution. we have seen as much as 15% of our server negotiate the wrong duplex with the switch ports.

I am looking for anyone that has experienced a slowdown in performance when going to Gigabit speed on HP server running Microsoft server 2003 connecting to Cisco 3750 switches. How they solved the slowdown issue.

pciaccio Tue, 06/12/2007 - 07:40

Try looking at your TCP window sizing. MAny users notice that an increase in bandwidth does not bring a performance increase. The TCP window size needs to be tuned for your systems. Look at the attach documents for reference... Good Luck, Please rate...



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