Slow gigabit

I have two gigabit enabled machines. The each have different motherboards, but both motherboards use the Realtek RTL8111D NIC. The machines are connected in this way:

machine 1
~15 feet of CAT6
D-Link DGL-4300 gigabit router
3 feet of CAT6
in-wall coupler rated for CAT5e
~50 feet of CAT5e
Rosewill gigabit switch
~15 feet of CAT6
machine 2

File transfers between the machines are slow. :(

I downloaded the PCATTP tool:
On one machine I run:
PCATTCP.exe -R 99999999
One the other I run:
pcattcp -t -f M
I see a speed of ~11MB/s (megabytes/second). If I run the second command on the same machine as the first (loopback), then I see 500MB/s.

There shouldn't be a problem mixing CAT5e and CAT6, and both can do gigabit.

To try to simplify the test, I replaced the Rosewill switch with a CAT5e inline coupler. I still see only ~11MB/s.

Do you think a cable or coupler is damaged? Should I get a tester tool? It seems if there was a bad connection or damaged cable that the connection would be reliable. I use the internet through machine 2 every day and it is fine.

Does anyone have any ideas on how to fix my slow transfer speeds? Both machines are running Windows 7 Ultimate, and both have Intel X25-M SSDs. I have set both NICs to 1gbps full duplex. Are there any other settings I should look at? Anything at all that could help?
5 answers Last reply
More about slow gigabit
  1. Does the router have the latest firmware?
  2. swap machine to test the current cabling.

    Have you looked thru the config and made sure its set to use gigabit instead of 10/100? Different mobo's often have different defaults.
  3. Yes, the router has the latest firmware, 1.8.

    Swapping the machines is a good idea. PITA, but a good idea. :D

    I don't remember any gigabit settings in the BIOS, but I'll check again.

    If I set the speed back to auto negotiate, machine 1 shows up with a link speed of 1000, but machine 2 shows up with 100. Both machines have the same NIC and are using the same driver. I have ordered a cable tester from the egg, something might be messed up since 10/100 uses 2 pairs and 1000 uses 4. I may swap the machines in the meantime, since that will give pretty good proof it is the cabling. It is just the servers are heavy, and there are 3 floors to carry them.. :p
  4. What are you using to test the transfer? It will not transfer faster than the hard drives support. Multiple small files also take a lot longer than a few large files. Let's just make sure to eliminate that as a possible issue.
  5. I described my testing procedure in the first post. Also, file transfers are slow even when both machines have an SSD.
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