openssh bugs - Oct 2004 - [Bug 946] scp slow file transfers, even with -1 -c blowfish

http://bugzilla.mindrot.org/show_bug.cgi?id=946

           Summary: scp slow file transfers, even with -1 -c blowfish
           Product: Portable OpenSSH
           Version: 3.8.1p1
          Platform: ix86
        OS/Version: Cygwin on NT/2k
            Status: NEW
          Severity: major
          Priority: P2
         Component: scp
        AssignedTo: openssh-bugs at mindrot.org
        ReportedBy: zippy at cs.brandeis.edu


I am using scp and seeing file transfers that are far, far below my wire speed.
Using the scp default settings, I get ~300kB/s on a 100Mb/s networks and a
10Mb/s network. Using ssh version 1 and blowfish I get 500kB/s-1MB/s, again on
both the networks.

I am running scp on Cygwin on a 1GHz Centrino x86 machine (Windows XP Pro SP2).
The process monitor reports the CPU on the sending machine is around 50%. In
transfering a 200MB movie (avi) I see the following stats:

$ scp 200MB-movie.avi foo at bar:/a/b
200MB-movie.avi       2% 4848KB 480.8KB/s   06:00

I see this with any destination machine on two different LANs: a Suse64 AMD64
with no load and a RAID5 array, a P133 FreeBSD box with no load and a single IDE
drive, and a Linux box with moderate load.

If I force scp to use ssh protocol version 1 and blowfish, I get better
performance but still far below wire speed:

$ scp -1 -c blowfish 200MB-movie.avi foo at bar:/a/b
200MB-movie.avi       7%   14MB 813.9KB/s   03:21 ETA

I ran top on one of the destination machines (Suse64 AMD64) and the CPU was
under 10%.

I do not have a .ssh config file.

$ ssh -v
OpenSSH_3.8.1p1, OpenSSL 0.9.7d 17 Mar 2004

Any suggestions or workarounds appreciated.

--Pat / zippy at cs.brandeis.edu



------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.

http://bugzilla.mindrot.org/show_bug.cgi?id=946





------- Additional Comments From dtucker at zip.com.au  2004-11-02 21:23 -------
Try Ciphers=arcfour it's usually faster than blowfish or aes if you're
CPU
bound.  Also, make sure you have compression disabled.

With my laptop (XP SP1, 1.3 GHz Pentium M, OpenSSH 3.9p1) on a 100Mb/s ethernet
I get 1.5 MB/s (aes128-cbc, 15% CPU) and 1.6 MB/s (arcfour, 10% CPU).  In my
case, it appears to be IO bound.

How fast can you push data across your network without SSH?



------- You are receiving this mail because: -------
You are the assignee for the bug, or are watching the assignee.