openssh unix dev - Mar 2003 - Transfer rate issues with OpenSSH SFTP Server - Verified on Mac OS X 10.2.X and FreeBSD 5.0

First, I have what I consider to be decent experience with SSH, and have
been running VanDyke's VShell SSH server for considerable time under
Windows 2000/XP. Recently, I have been working with Mac OS X and FreeBSD
and have been using OpenSSH 3.4p1 The sftp server seems to have major
issues when serving files, specifically, if one data stream is used the
transfer rates fluxuate between 80 and 200 KB/s. Keep in mind that this
is over a 100Mbit switched link. If multiple transfers are performed at
once over one login session, the transfer rates of both files increases
to 800-1000KB/s still below what it should be but substantially better.

Performing similar transfers in the other direction, using the VShell
sftp server and sftp clients on the other boxes, the transfer rate is in
the order of 3000-4000KB/s. These are all modern boxes that should
beable to do AES-256/Twofish at more than adequate rates to sustain the
transfer, so the only thing I can think of that would be causing the
problem would be some bug in the OpenSSH sftp server.

Any thoughts?

Thanks

-John

On Sat, 22 Mar 2003 11:58 am, John Stockdale wrote:
> First, I have what I consider to be decent experience with SSH, and have
> been running VanDyke's VShell SSH server for considerable time under
> Windows 2000/XP. Recently, I have been working with Mac OS X and FreeBSD
> and have been using OpenSSH 3.4p1 The sftp server seems to have major
> issues when serving files, specifically, if one data stream is used the
> transfer rates fluxuate between 80 and 200 KB/s. Keep in mind that this
> is over a 100Mbit switched link. If multiple transfers are performed at
> once over one login session, the transfer rates of both files increases
> to 800-1000KB/s still below what it should be but substantially better.
>
> Performing similar transfers in the other direction, using the VShell
> sftp server and sftp clients on the other boxes, the transfer rate is in
> the order of 3000-4000KB/s. These are all modern boxes that should
> beable to do AES-256/Twofish at more than adequate rates to sustain the
> transfer, so the only thing I can think of that would be causing the
> problem would be some bug in the OpenSSH sftp server.
>
> Any thoughts?
What sftp client are you using? I get consistent 2.8Mbps with OpenSSH client
&
server with arcfour cipher.

Also, please retry your tests with a recent version. In a couple of days, you 
have 3.6p1 to try...

-d

I have been dealing with they same problem for at least a year now, and 
probably should have brought it up sooner. I use OpenSSH at work and at 
home on Apple, x86 and Sun systems ranging from from a K6-III/400 to 
uber-v880s, and no matter what system I use or which user is tranferring 
files, the throughput I get from the sftp server is pathetic. I work 
around this problem by just using scp wherever possible, because scp 
does *not* suffer a noticeable performance hit.

If this is just a simple cipher selection option, it needs to be 
documented somewhere obvious, because users and sysadmins just are not 
aware of it.

-james

John Stockdale wrote:
> First, I have what I consider to be decent experience with SSH, and have
> been running VanDyke's VShell SSH server for considerable time under
> Windows 2000/XP. Recently, I have been working with Mac OS X and FreeBSD
> and have been using OpenSSH 3.4p1 The sftp server seems to have major
> issues when serving files, specifically, if one data stream is used the
> transfer rates fluxuate between 80 and 200 KB/s. Keep in mind that this
> is over a 100Mbit switched link. If multiple transfers are performed at
> once over one login session, the transfer rates of both files increases
> to 800-1000KB/s still below what it should be but substantially better.
> 
> Performing similar transfers in the other direction, using the VShell
> sftp server and sftp clients on the other boxes, the transfer rate is in
> the order of 3000-4000KB/s. These are all modern boxes that should
> beable to do AES-256/Twofish at more than adequate rates to sustain the
> transfer, so the only thing I can think of that would be causing the
> problem would be some bug in the OpenSSH sftp server.
> 
> Any thoughts?
> 
> Thanks
> 
> -John
> 
> _______________________________________________
> openssh-unix-dev mailing list
> openssh-unix-dev at mindrot.org
> http://www.mindrot.org/mailman/listinfo/openssh-unix-dev
> 
-- 
James Puckett
System Administrator
The Lamus Company
703-268-3109
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