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Reply-To: moss@cs.umass.edu
Subject: Re: SSH/SFTP Network Performance?
To: Jordan Geoghegan <jgeoghegan60@gmail.com>
Cc: cygwin@cygwin.com
References: <a45d39ab-93e1-41d5-22c7-40a61e355fd5@gmail.com> <d1353aaf-271a-ba2f-7de0-80ca15b18e01@cs.umass.edu> <d400c16f-ff95-68fd-335d-0bd8ee28e154@gmail.com>
From: Eliot Moss <moss@cs.umass.edu>
Message-ID: <115ae2df-da57-12ce-5c2c-2e77da50b548@cs.umass.edu>
Date: Fri, 23 Mar 2018 22:06:31 -0400
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On 3/23/2018 9:54 PM, Jordan Geoghegan wrote:
> Hi Elliot,

It's Eliot, but no matter ...

> What was your setup that allowed you to reach 500Mbit? How were you copying the files? Were you 
> using SFTP, SCP or rsync?

I think I said rsync.  It was over ssh.  I disable compression since I use this
to send large files that are already compressed.

> Was it a Cygwin to Cygwin transfer, or was there another OS involved?

Sender: Surface Book Windows 10 (very up to date).  Microsoft 1 Gb USB Ethernet adapter.

Other end: RedHat kernel 3.10.0-693.17.1.el7.x86_64 on a recently purchased Xeon
server made by Dell.

As I think I mentioned before, I found that for wireless transfer (which this wasn't),
to get better performance than recent drivers, I had to go to an somewhat old driver,
and also disable 5G, using only the slower rate.  Given that when I use wireless I am
often at home and have only 12 Mbps uplink from Comcase, using the slower wireless is
not a bandwidth problem.  However, something about the drivers still limits me to about
half the theoretical rate.  I get a very regular square-wave sort of pattern when
watching the transfer rate, with a period of almost exactly 10 secs.  Again, that is
only for wireless.  Ethernet, except at the very highest rates, hits the max and generally
stays there, e.g., 150 Mbps on the slower net from my office.

Regards - Eliot

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