Slower network speeds from Windows 2003 to Windows 2008

I have noticed an a situation where/client where network transfer speeds, though not "slow" are much slower from Windows 2003 > Windows 2008 vs. the other way OR from Windows 2003 > Windows 2003 or Windows 2008 to Windows 2008.

 Using the simple Lan Speed Test Shareware tool I get between 300-400 Mbps speeds between servers on the same Gig Switch EXCEPT when going from Windows 2003 to Windows 2008 when I only get around 150-200 Mbps,  I initially thought it may be improvements in Windows 2008 but that does not fly when you consider I get 400 Mbps between 2 Windows 2003 servers...I have tried disabling SMB along with several netsh commands on one of the Windows 2008 servers (and rebooted) but it does not change the result.

 Anyone run into something similar? If I do the test from a specific 2003 server to a specific 2008 serer, get my 150-200Mbps results, I ca then turn around and go on the same exact Windows 2008 server and test back to this same 2003 server and get 2-3X the speed going that way.  The Windows 2003 servers are varied with several different kinds of nics so it is an OS level problem I would think
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How are you transferring the files?  File copy to a share or ftp?
There's not so much of bandwidth from one machine to another, in gigabit networking.
It's full duplex and it's a connection between two points.
This means, if you can get 400mbps from one to the other, that is what you can get (which by the way is very low). I can repeatedly get 800+mbps using iperf on linux.

The only way this above information can break down, is in very rare circumstances. These include driver issues, physical issues such as ports, bad patch panel keystones, NIC issues, etc. It is technically possible to cause the issues you're seeing with software but it would be very strange to encounter it happening unintentionally.

Please tell us what the hardware is for these machines; this is quite an important piece of information for your case.
Actually for Windows its not that unusual to see OS issues like this.

Some of the new Windows  (2008, Vista, V7) have Window scaling enabled by default, so TCP/IP tunes itself better that older OS's (XP and 2003).

Then you have SMB V1 vs V2.  Windows 2003 and older use SMB V1, which is not as efficient as SMB V2.

As for getting 400 Mbps, that is actually the norm for a single stream when using 1500 byte Ethernet frames.  Typically in order to get above that you need to enable jumbo frames.  In most situations once you get to a 4K frame size you can typically push Gigabit Ethernet to its limit.
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Given he's mentioned a network speed test application (which I am not familiar with actually), and is reporting speeds in mbps I'm assuming he's talking about network speeds and not file transfer speeds.

In a raw machine to machine network transfers you should get over 800mbps, which you can find another post referring to this here:

" As expected, iperf reported consistent numbers around 940 Mbps, which is (almost) optimal for a gigabit LAN. The MTU size on all switches in the gigabit LAN was set to 1500."

And as I've mentioned I have repeatedly gotten over 800mbps in my last tests of a standard 1500mtu gigabit network.

The testing app you're using is not known to me so I can't vouche for what it's testing. But what I do know is that just sending packets and testing the throughout you should be getting 800+mbps. Personally I would find a tool that is showing you these metrics as it will not even be using SMB in the first place.
bubbler86Author Commented:
Thanks for the comments.  I had used iperf but quoting iperf examples can get confusing as people use different packet sizes but keeping it at the default windows size of 8KB I am getting about 400-450mbps (bandwidth, transfer speed is about 525 MB's) between the Windows 2008 Machines AND Windows 2003 to Windows 2003...I also get that figure oneway  when doing 2008 to 2003 but NOT when going the other slows down to about 250mbps. So the iperf results are exactly the same as the other tool I used.  

As to the comment about this being normal I was ready to accept that EXCEPT for the fact that I am getting the same exact higher speed in 2003 to 2003 it is not a 2008 feature, it is something else.  I am using a SMB grade GB switch that was in the $300 range so not top of the line but these numbers are not that bad either.  Not really worried about the numbers just curious/would like to figure out why the numbers are almost halved going just the one way between 03 and 08 (or Vista to 08 or XP to 08...same issue, no issue going from Win  7 to 08 so I am still stuck on it being an OS setting).  When I did turn off SMB the numbers between the 08 servers drop dramatically but nothing changed in the 03-08 server numbers.  I do not think it is hardware as these servers range from 1 year old to 8 years old, some are on Hyper-V, some are not...all are HP.  Regardless of virtual or not I am getting the same results.  Only common piece is the switch but not sure what setting would only affect 2003 to 2008 testing and not any other.
bubbler86Author Commented:
To add to this...I had time to do a little more testing this AM with a 150MB file and find the same issue.  Between 2 Windows 2003 servers or between 2 Windows 2008 server it goes in about 2 seconds @about 80 to 90MB/sec.  Copy it from Windows 2008 to Windows 2003 also goes in about 2 seconds.  However, copying from Windows 2003 to Windows 2008 drops to about 30-40MB/sec and takes twice as long.  
Also I noticed if I raise the windows on iperf to 48K, the speeds are equal between all servers regardless of OS (about 800-900 meg).  So this once again points back to OS and something to do with the protocal stack on the Windows 2008 servers in combination with TCP packet sizes the Windows 2003 servers are using but have not pinned it down yet.  

I have turned off anti-virus for all this testing so that is not an issue.  Actually uninstalled it on one of each OS to completely remove that from the equation.
It would still be interesting to see what a packet capture shows.  However even at "slow" 30-40 MB/sec you only need a couple of seconds.  

It's real interesting that 2003-to-2003 performs well, but 2008-to-2003 does not until the Window size is increased.  The only thing I can think of is that maybe something is being negotiated differently with ACK's.

As for everything getting 800 Mbps+ with 1500 byte MTU's.  Well, maybe a new system (new within the last couple of years).   Until recently the avg. computer's drives could not keep up with a sustained rate of 1Gbps.  Amazing as it seems, the hard drives were the slow point, not the network.   Then the was issues with CPU's.  Before hyper-threading and multi-cores (and a little while after), CPU's also had problems keeping up with the almost 90,000+ interrupts/sec needed to handle 1Gbps using 1500 byte MTU's and doing I/O to the "slow" drive.
bubbler86Author Commented:
I have found the cause of the slow down though not sure how I will apply fixes going has to do with SMB signing.  Changing the registry entry below to disable allowed the Windows 2003 boxes to transfer at the speed I was expecting.  "Apparently" this specific reg entry is only effective on SMB 1 packets so have to research a bit to make sure I do not leave an extra security hole open for the sake of speed...this specific Win 2008 is not a DC though.  Points awarded though based on getting me thinking in the right direction.  The extra overheard from the security was slowing down my test results.  May turn it back on, not sure, but at least I know the source now.  I knew it was OS related just could not pin down exactly why.


Value Name: EnableSecuritySignature
Data Type: REG_DWORD
Data: 0 (disable), 1 (enable)

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bubbler86Author Commented:
Using comments from other posters I was able to ascertain the proper solution and wanted it to be recorded as such if this is added to the knowledgebase.
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