I have 4-5 computers in my home network, connected via a 100Mbs switch.
The problem is they should be connected with 100Mbs, full duplex but when I copy files between any computers, speed is below 10Mbs.
It doesn't matter what distro I use (the same is also between Linux and Windows).

NIC's are all PCI (most of them rtl8139), cables are cat5e, carefully checked the spec for the switch. My first thought was that it was some hardwareproblem, but then all Linux's say at bootup, when initializing NIC, something like "...using 100Mbs full duplex based on negotiation with..."

This puzzles me, I have no clue where I should start looking? No lack of tools, but which can be used to check or change what?

P.S The speed is measured both with midnight commander and checking the taskbar-graph for eth0 (I use IceWM).

Does your switch has LEDs for 100MB/s capable devices? If so - are those leds on?

How do you transfer files (perhaps via scp)?

The switch doesn't have leads specifically for that, just shows connections.

Measured transfers done with ftp (proftpd or wu-ftpd) and nfs-mounts (normally).
Now that I think about it, logging in via ssh often takes some time before I get an answer. Could it be related? Mounting nfs-shares is done immediately, though, and still slow transferrates.
Might also add that 'ifconfig' shows no drops, collisions or other errors on any NIC.

Did you set up every IP in your hosts (/etc/hosts) table? Perhaps it has something to do with reverse DNS lookup, but that should normaly only affect initial login to a service and not datatransfer when logged in. Anyway, perhaps you try this.

No, I use IP's to connect, not names.

Off course you use IPs to connect, but the service tries to reverse-lookup your IP to get a full qualified name for your machine and if your machine doesn't have an own DNS to handle such lookups, then you have to provide those information manually by putting the proper records in /etc/hosts.

OK, my misunderstanding.
I believed that by only using IP's I wouldn't have to bother about names at all.
I'll fix that when I get home, thanks for that.

But that might solve only the secondary problem, not the low transfer-rates.

Yes, I think this should remove the lag at the beginning of a sesseion but not the low transfer rates (even just a little bit).

Are there only 100MB/s devices connected to your switch? Maybe it's a cheap switch which is more like a hub and then falls back to 10MB/s if there is one device connected that can only do 10MB/s.

That could be it.
It is a cheap switch, I was beginning to wonder if that "..setting 100Mbs..." could be trusted, but then there is one computer equipped with an old isa-nic. That computer is never the first I boot.
I'll return tomorrow with results!

You could always check if your cards stay in full 100mbps by running a tool named "mii-tools"

Running that will tell you the speed configuration of your NIC and then you can change it manually.

Also, don't forget there might be cable problems... Cisco guys say you could hardly reach 10 Mb/s if your cables run near power lines... even the rj45 sockets could be responsable for speed issues.
So, let's do a TODO thing:
1. check if it's a a 10Mb/s or 100Mb/s switch
2. check NICs speed rate
3. check cable condition

Good luck!

I had forgotten we were invited to dinner last evening, so I haven't had any time to check this yet.
The cabling is ok, I took care of that when I installed the network. Haven't given the sockets any thought, though.
(I was wrong about the computers, they all have 100Mbs nic's. But then there's a network printer connected which probably only is 10 Mbs.)

Well, you've given me some good hints. I'll check during the weekend, back on monday!
Thanks!

Ok, I now think that it is obvious that you've got an 100MBit/s Switch and not an 10/100MBit/s one. Yours will fall back to 10 MBit/s if there is one 10 MBits/s device (printer). Just unplug this device and then try again transfering files, if you get more than 10MBit/s, you'll have to buy a 10/100.

This is so weird!

First the good news: Secondary problem (long time to login) was easily solved using /etc/hosts. Thanks for that.

Now the funny part starts. My network:
Workstation 1 (aka edgar) onboard LAN, nvnet Mandrake9.1
Workstation 2 (aka tjabo) 3Com ISA 10Mbs Mandrake9.1
Server Realtek (PCI,8139too) RedHat 7.1
muzak Realtek (PCI,8139too) LibraNet/Debian kernel 2.2.? (as small system as I could get) Transferring using Knoppix (no ftp, ssh, nfs or anything in installed system.).
felan Realtek (PCI,8139too) Mandrake8.2
HP Laserjet , probably 10Mbs

edgar is the only computer in which 'mii-tool -w' keeps showing changes. Connected to the switch it always goes to 100Mbs FD, connecting directly to tjabo it goes down to 10Mbs. All the same, I removed the network cables for tjabo & printer and power-down'd the switch, then turned it on again.
For server and muzak 'mii-tool -w' shows 10Mbs FD, trying to force them to 100 doesn't change anything.
On felan message is 100Mbs FD.
On no realtek-equipped computer 'mii-tool -w' shows any changes when unplugging, reconnecting to faster/slower nic's. That is no new line in terminalwindow.
Transferrates:
edgar <-> server or muzak 30Mbps one direction or 2x 16Mbps
edgar <-> felan steady at 20 Mbps one direction or 2x 16Mbps

With c/o-cable edgar <-> felan, 'mii-tool -r' on felan keeps it at 100Mbps, then on edgar sets it to 10Mbps, again on felan now sets 10Mbps...
Forcing 100Mbps on both, edgar accepts, felan too but with a 'no link'-statement. No speed-difference, though.
That statement - 'no link' - is always at server & muzak.
While trying to speedup server (using mii-tool), it once started copying at almost 100Mbsp, directly down to 45 Mbps and a few seconds later it went down to 30Mbps and stayed there.

Conclusions
1. mii-tool has done something, speed is higher now than before. Far from 100Mbps though.
2. server + muzak does not run in full duplex. felan could, but 20% loss is a bit too much?
3. Main conclusion: No Realtek card works as it shall.
4. Switch is a 10/100 (not 100% sure, but almost)
5. The "ordinary" cables + wall-jacket are cheap stuff, the crossover cable is not. There is no difference, I don't believe there's a cable problem.

I believe the problem is those 10$ Realtek nic's.
If nobody has some other suggestions, I'll buy a new nic (want to replace that ISA-nic anyway) not staring at the price this time. I believe 20$ or so will be enough to assure decent quality.
Then I will have at least 2 computers reaching full speed, making problem-solving a lot easier.
I have no time for this now, will take a week or two.
If I don't solve the problem then, you'll hear from me again.
Thanks, everybody!

I have now tried with a NetGear nic. Didn't help, but got more info:
I can't use mii-tool on this card - "operation not supported"
Interesting is that when I start transferring files I get rates of 40Mbps one direction, 20 Mbps in both directions. ifconfig on server now reports lots of overruns. I run 'mii-tool -r' on edgar and it sets 10Mbps HD! Transferrates drops, no more errors.
So server refuses to go higher than 10/HD.
Why is that? RedHat7.1 shouldn't have a problem with 100Mbps?
(I am soon to install Mandrake 10 on felan, will try with NetGear card there. I doubt it'll do any difference.)

Any ideas?