fartness
Computersoc Dot Com
Premium
join:2003-03-25
Look Outside
clubs:
3 edits | Why is gigabit slower?
Here is the setup. I have computer 1 with gigabit ethernet and a 1TB WD Black (32MB buffer, SATAII). Computer 2 has a 133MB/s IDE hard drive and gigabit ethernet.
Both computers are plugged into a D-link gigabit switch. I get 50mbps (yes, 50 megabits per second). If I plug both computers into my 10/100 router, I get the 100mbps minus the usual overhead. This switch has always done this on any gigabit capable computer, but why!? It should sustain at least 100mbps when using the gigabit switch if it goes that speed when connected to the 10/100 router.
Both computers also have WD Raptors, but I haven't tried benchmarking them yet.
The files I am testing are less than 1GB (around 150 to 600MB) when the speed is 50mbps on gigabit and 100mbps on the 10/100 router. When I test a 2GB file, I get a sustained 430mbps going from the IDE drive on the one computer to the 1TB drive on the other computer. I get a sustained 560 mbps going from the 1TB drive on the one computer to the Raptor on the other computer. It still shouldn't matter the size of the file or the hard drive, because it gets close to 100mbps when I use the router, but it only does 50 mbps on the switch.
I don't think it could be fragmentation either, because I should still get a sustained 100mbps+ with the switch if it did it with the router.
I should also note it doesn't "stay" at 50mbps with the switch. It fluctuates but the average is around 50mbps. It still goes above 100mbps sometimes, but rarely. Usually stays around 50mbps. With the router, it stays at the same speed. |
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fartness
Computersoc Dot Com
Premium
join:2003-03-25
Look Outside
clubs:
| Setting it to transfer 1 file at a time seems to be the solution, but it doesn't explain the difference still between the 10/100 router and the gigabit switch.
Also, why do I get 700mbps sometimes and with the same file again I will only get 430 like I usually do? |
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JohnInSJ
Premium
join:2003-09-22
San Jose, CA
 ·Comcast
1 edit | reply to fartness
Never use file copy to test lan speeds - way way too many variables.
Run iperf on both computers, one as client, one as server.
Let us know what you find.
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My place : »www.schettino.us |
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fartness
Computersoc Dot Com
Premium
join:2003-03-25
Look Outside
clubs: | I'm not really testing LAN speeds. I'm just pointing out that I'm getting 50mbps when transferring multiple files using my gigabit switch, versus close to 100mbps when transfering files using my 10/100 router. |
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JohnInSJ
Premium
join:2003-09-22
San Jose, CA
·Comcast
| You are testing lan speeds 
There is an issue with your switch, or one or both giga cards. You could diagnose it with iperf. Other then seeing it, you can't really diagnose anything by copying files.
Brands of cards, switch? OSes used?
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My place : »www.schettino.us |
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Leathal
Premium
join:2002-02-09
Toronto, ON | reply to fartness
Robocopy works great for LAN transfers, it's by Microsoft.
L. |
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