[PLUG] Incredibly Slow scp Across Local Ethernet

[Terry Griffin]

On Fri, Jan 09, 2004 at 01:03:01PM -0800, Paul Mullen wrote:
> The subject pretty much says it all. I've got two local machines (both
> Linux) directly connected via a cross-over cable. On one side is an 800
> MHz PPC, and the other a 120MHz Pentium. Networking seems to operate
> just fine, for the most part. I can ssh in to the Pentium from the PPC,
> and do all the usual shell-ish stuff. Transfering files via scp is
> unbearably slow, though. After the first ~500k the connection begins to
> "stall" (as reported by the scp status line), and never seems to make
> any further progress. Small files seem to be OK, but I've tried a 15 MB
> file and a ~300 MB file, both with no success. Any ideas? I've tried a
> Google search, but couldn't figure out an appropriate query for the
> question. :-/
> 

scp's built-in progress bar is highly misleading. I suspect it's not
accounting for local buffering. I notice this when I'm transfering over
a 56K modem link. The transfer starts out absurly fast for 56K, then
it "stalls" when in reality it's just grinding along at modem speed.

I suggest you use some other tool to get a better sense of actual 
throughput while scp is running. I like the xnetload and iftop utilities. 
Search for them at freshmeat.net.

Terry
-- 
Terry Griffin <griffint at pobox.com>
http://www.blindchicken.com/~terryg/