[clug] SCP from Windows to Linux incredibly slow

paul at pabryan.mine.nu paul at pabryan.mine.nu
Tue Aug 3 02:59:10 GMT 2004

On Tue, Aug 03, 2004 at 10:31:33AM +1000, Paul Wayper wrote:
> Caller number ten on the help line asks:
> I'm trying to copy some files from my Windows 2000 machine (tangram) to my 
> Fedora Core 2 machine (ludos) via SCP.  I'm using both pscp (of the PuTTY 
> family) and WinSCP; both are incredibly slow - in the order of bytes per 
> second.  The two machines are on 100Mbit network cards, both mostly idle 
> (except for distributed.net, which I have tried stopping to no effect).  A 
> copy in the other direction - dragging a file from ludos to tangram - goes 
> at 350KB/sec - much faster than the direction I want yet still much slower 
> than the theoretical peak network speed.

Duplex mismatch on the network cards? I've seen similar problems
(slow transfer one way, fast(er) transfer the other way). 

Usually, by default, most cards/switches/hubs will auto-negotiate the
best speed. I've seen a number of switches where this just doesn't
work, so you need to statically set the speed and duplex.

My suggestion would be to set both to 100Mbps/half-duplex. Under Linux
you can use mii-tool or ethtool to do this. Under Windows, open you
network properties, click around for a while and you should find the
appropriate place to configure these settings. (I'm pretty sure that's
the official procedure ;)

You may also need to set things on the switch/hub depending on the
particular device.

If it works at 100Mbps/half-duplex, try full-duplex and see what happens.


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