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

[Cary Jamison]

Max Stein wrote:
> 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.

This was discussed on cygwin-xfree a few months ago - Holger Krull posted a 
message with a link to a patch to improve things :

http://sourceware.org/ml/cygwin/2005-11/msg00897.html


Cary




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

[Hannu E K Nevalainen]

> Ah, so your first MB was Megabit and the others were MegaByte...

To get it straight, and for the archives:
 http://en.wikipedia.org/wiki/MB - overwiew.
 http://en.wikipedia.org/wiki/Bit lower case "b", also @ "More than one bit"
 http://en.wikipedia.org/wiki/MiB - UPPER case "B" here.

Another similar issue:
 http://en.wikipedia.org/wiki/Baud
 http://en.wikipedia.org/wiki/Bits_per_second

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

[Arend-Jan Westhoff]

At 22:52 2006-03-18 +0100, Max Stein wrote:
>> 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.

Unfortunately neither am I. It was an idea derived from a report on the
stunnel 
program:

that tunnels through SSL and according to the report can do such aggregation.
(I don't know an english version of this report so I'll refrain from
providing a 
link to that.)
Since neither the CPU nor the network bandwidth is fully used in your case
it would seem at least theoretically possible that the same could be done
with 
transport over SSH. I formulated it as a question because I am not absolutely 
sure and don't know the details myself.


>> 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.

Ah, so your first MB was Megabit and the others were MegaByte...
To prevent any more misunderstandings: Are you talking about the 
Windows FTP or the Cygwin FTP here?
Anyway, it seems not too far fetched to assume that anything that runs 
directly on a native (i.e. Windows or Linux) OS would outperform a similar
thing running through an emulation layer (Cygwin).

Arend-Jan Westhoff

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

[Kevin K]

On Mar 17, 2006, at 7:49 PM, Max Stein wrote:

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



For what it is worth, I've also noticed his using the Putty tools,  
including Putty's scp client.  At first I thought it had to do with  
my wifi connection, but even when both computers were connected  
directly to a switch together, it was much slower than I would have  
expected.


The numbers you quoted above are in the ballpark of what I've  
measured with Cygwin's clients.


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

[Arend-Jan Westhoff]

At 02:49 2006-03-18 +0100, Max Stein wrote:
>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.
>

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

HTH,

Arend-Jan Westhoff.

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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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