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Ethernet Speeds

Posted on 2004-08-03
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Last Modified: 2010-04-11
I have two computers connected directly to each other via a crossover cat-5/ethernet cable.  Both NICs are set at 100Meg/Full Duplex (not auto-detect), but I'm only getting about 1.7 MB/sec transfer.  Why is my rate so slow?  If I have 100baseT, shouldn't I be getting in the neighborhood of 12.5 MB/sec?
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Question by:lofiched
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by:grblades
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Hi lofiched,
Yes you should be getting a much faster speed. A more typical speed would be between 11-12MB/s
What spec are the machines?
Perhaps the hard disks cannot keep up if they are old?
Have you tried a different cable?
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by:lofiched
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Tried different cable, no fix.  One machine is a new (less than a year) Dell, the other is an older HP LH3 Server, but it's running dual 400MHz and uses 10,000 RPM SCSI drives.  I'd think that would be able to keep up without any problem.  Also, right now, these two machines aren't doing anything expcept the transfer.
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by:grblades
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How are you testing the transfer speed?
Between what two applications?
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by:lofiched
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doing a large file transfer and using performance monitor to watch network interface 'bytes sent'.  Perfmon reports an average of about 1.7MB/s, a max of about 2.3MB/s, and a min of 1.1MB/s.

Also, it took between 2 and 2.5 hours to transfer a 14GB file, which if you do the math, comes out to somewhere between 1.5 and 1.9 MB/s.
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by:grblades
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Do you have a 3rd machine you can experiment with?
I would connect the 3rd machine to each of the other two in turn and check the transfer speed to see which one is having a problem.
Then you can try changing the network card etc... on the affected machine.

I assume you were transfering the file via normal windows file sharing?
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by:lofiched
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I can't really experiment right now.  The server is one of our Exchange servers and we had to rebuild one of the arrays and now we're moving our saved databases back to that drive.  Anyway, I can't mess with it at all , really, because it's been down for 2 days and people are getting antsy.  Then, of course, once it's up, I won't be able to take it down to test it.  

I was kinda hoping someone new of a reason off the top of their head, assuming all normal troubleshooting practices have already been executed.  For now though, I guess we'll just have to live with it.  Maybe some night, on like a weekend or something, I can take it down and check it out some more.
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by:ocon827679
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Can you try setting it to Half/Duplex?
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by:lofiched
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Unfortunately, no.  I can't do anything that will disruspt the file transfer.  As it stands right now, it's gonna take between 6 and 8 hours to complete the transfer, and if have to start it over, I know I will be called in to talk to people I don't want to talk to.
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by:ocon827679
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drag dude - understand your predicament!
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by:Kooroo
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check fragmentation of your volumes. I had a server on channel bonded 10/100 FD NICs putter around at like 5Mbps once because of massive file fragmentation.
I *think* you could get a fragmentation report without disrupting the transfer, diskkeeper analysis is usually a safe thing to run.

man, I sympathize with you tho.
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by:ErikPhilips
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I had a similar incident.  Manually changing my cards from auto to half duplex fixed the problem.  I’m not happy about doing it, but it’s a good temporary solution, after all I get 100mbit speed vs the same thing you are seeing.
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by:scottman29
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I don't really think it's a harddrive issue.  I'm not saying that the harddrive couldn't be a bottle neck, but if you think about it, the hard drives should be able to keep up with NIC's, they are usually a bottleneck when being accessed directly like a database or something.

I was curious if it could be a protocol issue, or a bind order issue.  You would need a network monitor to really test and see if there is any type of translation going on.  However if it's all windows, then that really shouldn't be an issue.  Are you running any sort of compression or encryption?

-yours, Scott
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by:lofiched
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I need to check the fragmentaion, but I Have higher priority things going on right, like complete site public folder restore...but that's another story.

I also want to try switching to half duplex, even though that doesn't make much sense to me, but you're the second person I've seen say that.

Both systems are all Windows.



BTW - The recovery of that server went off without a hitch, aside from taking like 10 total to complete.
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by:PennGwyn
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Although you can set both cards for full duplex, as you've done, that doesn't always guarantee the result you want.  I had a case here recently where if I set the switch to auto, it would negotiate a fast full-duplex connection with the server, but if I set the switch to full, throughput dropped to a trickle.  I think the server was a DEC/Compaq/HP box....

The other common cause I've seen of poor Ethernet performance has been damaged/defective cables.  You might try replacing that crossover and test again.

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tropsmr2 earned 30 total points
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PennGwyn is right.  I highly suspect that one of the NIC cards is not actually fixed at 100Full.

Ethernet negotiation is probably one of the most misunderstood protocols in networking.
(nor was it really spec'd well either, but that's another story).

When setting for auto, both sides MUST be set for auto.  Negotiation is a two way street here.

With one side set for auto, the other fixed (half or full), the auto side has no partner to negotiate with and will default to HALF.  So, if one side is FULL and the other AUTO, then you end up with FULL and HALF.

When you end up with FULL and HALF, you get really poor tput.  The number of dropped packets have little bearing on low-load protocols like ping, but are death for transfer-intensive applications like FTP.

I cannot tell you the number of times I have seen this during my career, nor how many bugs I've filled with Ethernet hardware engineers for their bad negotiation code :-(.

Try setting both to auto or half.  Beware, you may have to take the link up and down in order for the changes to really take place.  Again, you shouldn't have to, but it depends on how the engineer coded the MAC.

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by:ErikPhilips
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>tropsmr2

Interesting.  Maybe I should update my drivers.  The weird part about my problem was that when I copy a file TO the server its slow, really slow.  When I copy a file FROM the server, its normal speed (fast).  Setting Half duplex fixed it, which doesnt' make sense to me.  It also happened after upgrading Win2000SBS to 2003.  Setting it to Full Duplex didn't fix the problem.  I'm going to look into replacing my Netgear Switch, see if that fixes it :)  (ps. it was manually set to 100).
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by:tropsmr2
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Sounds like you are getting closer.  The fact that the problem is directional can make sense.  Data transfers are traffic-heavy in a unidirectional fashion - one directions has large packets going one way, the ACKs are a very small stream (like pings) going the other way.

I've sorta lost the configuration you are talking about. Thought it was back-to-back x-over; where did the switch come from :-)

Anyway, the fact that it works when you set one side to half tells me that the other side probably wasn't actually at full (it was probably at half).

Now that we know it works at half, you might want to try both at auto before changing the infrastructure.  Upgrades to the NIC drivers may also give you some relief.

I'd like to hear more about the actual configuration, including the switch.....

t
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