Transfer rate issues with OpenSSH SFTP Server - Verified on Mac OS X 10.2.X and FreeBSD 5.0

James Puckett jpuckett at
Tue Mar 25 04:45:20 EST 2003

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.


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

James Puckett
System Administrator
The Lamus Company
"...They have as king over them the angel of the bottomless pit; his 
name in Hebrew is Abad'don..."
~Revelation, Chapter 9, Verse 11
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