Re: sshd and scp/sftp: slow throughput on windows machines

[Max Stein]

1. Is it possible to increase the bandwith by having the client aggregate
multiple sessions through a single pipe?


Could you please give me some advice how this can be achieved? I am not an 
SSH guru yet.



2. It would seem that PPTP connections can be much faster. E.g. a FreeBSD
MPD running on a 400 Mhz Pentium II can sustain a 50 Mbit/s datastream at 
a

CPU usage of 25%.
W2k and XP have easy to configure PPTP clients.
(See also W2003 RAS.)


Why should a point to point tunnel improve the performance? Using Linux on 
the client and server machines I achieved a throughput of 10.8 MB/s whereas 
the theoretical maximum on a 100 MBit/s ethernet network would be 12.5 MB/s.


There must be another way. Why is the Linux implementation of SSH able to 
provide a much better throughput for scp/sftp
than cygwin's implementation running on the same hardware? It is not a 
problem of the Windows operating system because usual FTP tranfer yields 
simalar fast throughput of 10-11 MB/s like SSH running on Linux.



Max Stein 



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sshd and scp/sftp: slow throughput on windows machines

[Max Stein]

Unfortunately, the performance of the cygwin sshd server is very poor when 
it comes to copying large files. I have made this observation on several new 
and fast machines (3 GHz, 512 MB RAM, 100 MB/s Intel Pro network card) 
running with Windows XP or Windows 2003 Server. The best speed achievable 
was about 4 MB/s when copying a file from the SSH client to the SSH server; 
when doing it the other way round, the throughput was even worse, about 2.3 
MB/s. I tried it on three different machines running the newest version of 
cygwin's sshd und scp/sftp. The results were approximately the same.
Neither the client's nor the server's processor was really busy. The CPU 
usage oscillated around 30-40%.


Setting up the same scenario on linux yielded a completely different 
picture. Using the Knoppix disc 4.0.2 on the client and the server machine I 
easily achieved a throughput of 10.8 MB/ in both directions (pushing a file 
to the server or downloading a file from it).


What could be done to improve the performance of cygwin's SSH server? There 
were already some older posts dealing with the same problem but nobody had 
really a constructive idea or proposal.



Max Stein 



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