SSH/SFTP Network Performance?

[Jordan Geoghegan <jgeoghegan60 at gmail dot com>]

Hi folks,

First time poster here. I was hoping others could weigh in with their 
experiences running an ssh/sftp server from Cygwin.

tl;dr

Has anyone ever successfully transferred 150Mbps or more over the 
network using scp/sftp/rsync etc on Cygwin?

For a more in depth explanation, see below:


I have been experimenting with transferring data from my Windows 
machines through various methods, and was hoping to use rsync as that is 
what I use for backing up my other machines. During my testing, I have 
unfortunately been unable to push more than ~8MB/s (~60 megabits per 
second) regardless of the cipher (aes-gcm, aes-ctr, chacha20 etc) or 
transfer method (scp, sftp or rsync). All of them seem to be hitting 
some sort of bottleneck, with sftp being marginally faster than the others.

I am backing up to an OpenBSD file server on the local LAN. Using 
OpenBSD ---> OpenBSD (or Linux, MacOS etc) I can saturate the 1Gbit 
interface no problem. When using the built in Windows file sharing, I 
can also saturate the interface.

The fastest ssh transfer speed I have managed from Windows has been 
using various proprietary offerings such as the Bitvise ssh server or 
the SSH NetDrive sftp network drive mounter utility. Both of these tools 
also seem to hit some sort of bottlneck, though around ~18MB/s (~150 
megabit max as per Task Manager) for Bitvise, and around ~24MB/s (~200 
megabit max) with SSH netdrive.

Task Manager shows less than 5% cpu and disk usage, with only a slight 
bump up to 7% when using chacha20, I presume due to the lack of AES-NI 
for chacha. The machine is an i3 with an SSD and an Intel NIC so I am 
scratching my head as to what the issue could be. Cygwin will saturate 
my my 150Mbit WAN link in any direction over https no problem as well, 
which is interesting.

So, that's my story. Has anyone had any luck pushing beyond 150 megabits 
via ssh from/to Cygwin?



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