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SLOW Gigabit LAN

Last response: in Networking
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March 15, 2011 11:06:01 AM

Hello, I have a Gigabit lan, configuration is:

PC1
win 7 64bit + Intel 82577LC Gigabit Network Adapter

PC2
win 7 64bit + DGE-528T Gigabit Network Adapter

PC3
ubuntu 10.10 64bit + Realtek RTL8111/RTL8168 Gigabit Network Adapter

SWITCH
DGS-1008D Gigabit Switch

CABLES
brand new cat6

But the maximum file transfer speed I can get between all PCs is 40MB/s with windows sharing (or samba) and 50MB/s with FTP.

How is this possible?? Is there something I need to configure out?

Thanks!

More about : slow gigabit lan

a b X LAN
March 15, 2011 12:10:15 PM

Just because the network is capable of Gigabit speeds, doesn't mean your HDs are. While I would expect better than 40MB/s w/ a modern HD, I obviously don't know if these are indeed modern HDs. It's also possible anti-malware software can slowdown these transfers as it examines the files in detail, looking for viruses, trojans, etc.

In short, using file transfers as your measuring stick for network efficiency is generally not a good idea. There are just too many other issues involving file access that can mask your true network performance.

Instead, you should be using tools like NetCPS, Iperf, Qcheck, etc., that simply pump raw data from their buffers across the network. You’ll get far more meaningful and accurate results.
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March 15, 2011 12:23:01 PM

Thanks, I have tested the HDs as well and all are capable of 100MB write and read.. Testing the network with Iperf -w 64k the results were pretty good: ~950Mbit/s...

I'm measuring network speed with file transfers since that is what I need! I would love to achieve a transfer speed of 90-100MB/s....

P.S.
I'm not using any particular anti-malware software, just common ativirus.. And also transfers to Ubuntu via FTP are not scanned by any process i think...!
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a b X LAN
March 15, 2011 12:27:05 PM

~950Mbps w/ iPerf? Good, but then maybe the title of your post should really be "Slow file transfers" because clearly the Gigabit LAN itself is not the issue. :) 

Btw, you'd be amazed how much anti-malware (and that includes anti-virus w/ realtime checking) slows down file transfers. That's the first thing I look for when ppl report slow file transfers.
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March 15, 2011 12:35:13 PM

Mhhh... :??: 
Is I get ~950 when i use the -w 64k option, but just ~360 with no option... I googled deeply to find some tweaks but none seemed to work!
So is it necessarily due to the HD? I'm just testing them and the slowest (of the 3 pcs) has average write and read speed of 80MB/s...
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a b X LAN
March 15, 2011 1:10:50 PM

Since the Iperf -w options controls the tcp window size, I assume this is the issue. You may need to find a "tweak toy" that allows you to change the default/global tcp window size.

Beware, sometimes changes of this type can have negative side effects. So what might be good for large files transfers, might be bad for smaller file transfers. Or might lead to compatibility issues w/ say, your router. Tcp windows size isn't something I futz with, so I can't say for sure. But usually the default is the default for a good reason.


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March 15, 2011 1:18:37 PM

Yeah already done that, but it seems it is not possible to change that value in Win 7..! By the way, using FTP should not have anything to do with TCP window size..

Bahh! I'll just probably give up ;(
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March 16, 2011 3:12:28 AM

are you trying to transfer large unfragmented files? If you try to transfer files that cause any amount of random access, your speed is going to drop like a rock.

You've already tested your network and your HD, but you haven't tested the filesystem+SMB

Easiest way to test would be to use an SSD or ram drive. Even a small 1GB ramdrive would be enough to get a good average transfer speed.
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March 16, 2011 8:01:43 AM

Impressive man! I didn't even know about this RAMdrives! Test with ram drives on both PCs went ultrafast, up to 100MB/s...
So at this point.. What could it be the cause?

P.S.
Thanks all for the great advices!
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!