Subject: Re: rsync very slow, but not a network issue
From: Brian Dessent <[email-masked]>
To: cygwin <[email-masked]>
Date: Mon, 12 Jul 2004 22:15:00 -0700

Reini Urban wrote:

> > When the file is alredy there, rsync reports a speedup of about 70.
> > (When the file is not already there, the speed up is 1, of course.) I am
> > running rsync over ssh with pre-generated keys installed in my .ssh
> > directories.
> 
> This is a binary MP3.
> rsync (as diff) is not good in checking binary diffs.
> Please try it with a typical text file, where the patch
> is smaller than the source.

That is not correct at all, and rsync would be much less useful if it
were true.  rsync works with arbitrary binary data just as well as it
does with text.  It has no conception of 'lines' or any other type of
delimited text.  All it does is split up the file into fixed-length
chunks and calculates a rolling checksum of each of these.  It does not
use anything resembling 'diff' or 'patch'. 

http://rsync.samba.org/tech_report/node2.html

Brian

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