[Bug 946] scp slow file transfers, even with -1 -c blowfish

bugzilla-daemon at mindrot.org bugzilla-daemon at mindrot.org
Thu Oct 28 14:34:59 EST 2004


           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

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