Slightly OT - SFTP versus FTP speeds

Marius Gedminas marius at
Thu Sep 24 11:59:50 UTC 2009

On Thu, Sep 24, 2009 at 11:14:44AM +0100, Steve Flynn wrote:
> On Thu, Sep 24, 2009 at 11:06 AM, Steve Flynn <anothermindbomb at> wrote:
> > I know many of you use SSH to securely leap from machine to machine.
> >
> > How many of you utilise SFTP and vanilla FTP though? If you do, what
> > kind of speed difference do you witness in throughput?
> As I was about to say, vanilla FTP hits around 4.4Mb/s.
> The same file, over the same circuit when being sent via SFTP
> (Blowfish encryption, compression off) manages a rather disappointing
> 300 K/s.
> Processing power is not an issue - one end is a Windows VM machine and
> the other end is a pretty heft AIX server. The two are obviously
> running different implementations of the encryption stack (OpenSSH on
> AIX, not sure about the Windows VM machine). We are about to begin
> trying different SSH stacks on the Windows machine to rule out any
> oddball incompatabilitis  but if I can get some indication that the
> results I'm seeing are "off" then I'd appreciate it.

Your results sound plausible.  IIRC the highest transfer speed I ever
saw scp achieve was about 1 megabyte per second.  I don't recall if that
was on 802.11g wifi, or on 100 Mbit/s Ethernet.  Different SSH clients
also perform differently (the old gnomevfs SSH implementation was 2x
slower than scp on the command line).

I recently stumbled upon this page, which explains why SSH/SFTP performs
not very well and how to fix it (eventually):

Marius Gedminas
> I'm not sure what makes a given poem 'modern'...

Well, one characteristic sometimes found is... to put it politely...
creative typography.  Very creative typography.
	-- Henry Spencer on the chores of typesetting modern poetry
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