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From:	Johan van den Berg <johan DOT vdberg AT playsafesa DOT com>
To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Date:	Wed, 11 Jan 2012 08:25:02 +0200
Subject:	Re: socket performance (was Re: Building cygwin1.dll)
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On 10 Jan 2012, at 4:45 PM, Corinna Vinschen wrote:

> What Windows versions are we talking about?  Is that pre-Vista?  XP,
> for instance?  If so, setting the buffer size > 64K should have no effect.

Destination Windows: Windows Server 2008 R2 Standard 64bit (Intel Xeon) 
Destination Linux: Linux 2.6.32-71.el6 x86_64 (CentOS 6.0 Final)
Source Windows: Windows Server 2008 R2 Enterprise 64bit (Intel Xeon)
Source Linux: Linux  2.6.18-238.12.1.el5 x86_64 (CentOS 5.6 Final)

Also tried a source Windows 2000 with same effect.

> I really don't know why the performance should be so much worse than
> under Linux in your scenario, sorry.  Cygwin is not trying to do
> anything fancy.  The speed should be basically in the same range as on
> Linux.

Which means the culprit is windows (as was expected)...

> At least it is for me when using sftp.  When using scp I just found that
> I get a similar bad performance, only 6.9 MB/s instead of 35 MB/s.
> 
> Is it possible that the limiting factor is not the socket, but the pipes
> between rsync and ssh, assuming you are using rsync over ssh?

I was using rsync raw without ssh. I get the feeling I will need to read sftp's code now ;) Either sftp is setting something special on the socket options that scp / rsync is not, or sftp employs parallel connections. The main reason for using rsync is consistency of data and automation of mirroring, so it is by far the best tool for the job if you want 100% data integrity (unless someone else knows of a better tool for the job).
--

Kind regards
Johan


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