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We have a network with what seems like 100MB equipment everywhere but there are problems with the slow network. I tried to do a simple test to test the speed. From a Win7 computer I mapped a drive on the Win 2003 server with a 100MB switch between them (Trendnet 10/100 8PT w/4pt POE I believe is the exact model). The mapped drive had a 3GB file on it and I copied it to the local drive.

The 'detailed' copy dialog box reported a speed of a fairly consistent 11MB per second. I wouldn't expect the speed to be 100MB but I would think it would be faster than 11. The only other component is the actual Ethernet cable itself isn't it? Could that make a difference? What possible bottlenecks would cause this?

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No such thing as 100MB network gear... it's 100Mb, which is 8 times slower. –  Chris S Apr 10 '11 at 2:18
    
Chris: GigE ;-) –  Joris Apr 10 '11 at 8:14

3 Answers 3

up vote 5 down vote accepted

First thing, Network speeds are measured in Bits, and not bytes, so you network of 100 mbps is about 12.5 megabytes per second maximum. So if the 11 is bytes and not bits, then that explains it.

However if 11 is bits then:

Possible impact on the speed can come from how the network cards are setup, OS overhead, and drive read/write speeds. Also the PC's speeds and other processes utilizing the network and disks.

If the network cards are set for full duplex, i believe that would limit the maximum network speed to 50 mbps in either direction (i could be wrong).

If the drives and the machines on either end are older and running new operating systems, the bulk of the machines abilities are already tied up (thinking P4 circa 2004 running win 7).

Another factor could be the copy program you are using is measuring only the file data being transferred, and not the packet overhead.

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It must have been showing the progress in Mbytes and not Mbits. I'll check when I get back to a Win 7 machine. Thanks. –  Jeff Apr 11 '11 at 1:55

Terminology differences!

Network equipment, such as switches and routers, express speed in terms of bits (100 megabits per second). Network transfers, on the other hand, are usually expressed in bytes (11 megabytes per second on your test transfer).

You're essentially saturating the link; 12.5 MBps is the theoretical maximum for 100 mbps gear.

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so looks like my speed is as should be expected. Thanks –  Jeff Apr 11 '11 at 2:04

You should ensure that the duplex settings on your switches and hosts match. If one end of an Ethernet link has been set to 'negotiate' and the other set to 'fixed 100/full' then there will be a mismatch causing collisions, which will definitely slow down network traffic.

@jimsmithkka In theory a full duplex 100Mbps should be able to support 100Mbps each way, that's the meaning of the 'full duplex' part. Due to PC I/O limitations achieving 70/80Mbps for a file transfer would be quite acceptable.

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i couldn't remember fully at the time, i just recall full duplex meaning both ends have the ability to pass traffic at the same time (although that might be mistaken), and half-duplex meant one side could transmit at full at a time, meaning the other side would need to wait for the line to clear. The class i had for this was circa 2006, and haven't had a run in with it yet professionally. –  Jimsmithkka Apr 10 '11 at 8:05

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