<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><!--Converted with LaTeX2HTML 98.1p1 release (March 2nd, 1998)originally by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan* with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --><HTML><HEAD><TITLE>The rsync algorithm</TITLE><META NAME="description" CONTENT="The rsync algorithm"><META NAME="keywords" CONTENT="tech_report"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"><LINK REL="STYLESHEET" HREF="tech_report.css"><LINK REL="next" HREF="node1.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html4" HREF="node1.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next.gif"></A> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up.gif"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous.gif"> <BR><B> Next:</B> <A NAME="tex2html5" HREF="node1.html">The problem</A><BR><BR><!--End of Navigation Panel--><P><P><P><H1 ALIGN="CENTER">The rsync algorithm</H1><P ALIGN="CENTER"><STRONG>Andrew Tridgell Paul Mackerras<BR>Department of Computer Science <BR>Australian National University <BR>Canberra, ACT 0200, Australia</STRONG></P><P ALIGN="LEFT"></P><P><H3>Abstract:</H3><DIV>This report presents an algorithm for updating a file on one machine to be identical to a file on another machine. We assume that the two machines are connected by a low-bandwidth high-latency bi-directional communications link. The algorithm identifies parts of the source file which are identical to some part of the destination file, and only sends those parts which cannot be matched in this way. Effectively, the algorithm computes a set of differences without having both files on the same machine. The algorithm works best when the files are similar, but will also function correctly and reasonably efficiently when the files are quite different.</DIV><P><P><BR><HR><!--Table of Child-Links--><A NAME="CHILD_LINKS"> </A><UL><LI><A NAME="tex2html6" HREF="node1.html">The problem</A><LI><A NAME="tex2html7" HREF="node2.html">The rsync algorithm</A><LI><A NAME="tex2html8" HREF="node3.html">Rolling checksum</A><LI><A NAME="tex2html9" HREF="node4.html">Checksum searching</A><LI><A NAME="tex2html10" HREF="node5.html">Pipelining</A><LI><A NAME="tex2html11" HREF="node6.html">Results</A><LI><A NAME="tex2html12" HREF="node7.html">Availability</A><LI><A NAME="tex2html13" HREF="node8.html">About this document ... </A></UL><!--End of Table of Child-Links--><BR><HR><ADDRESS><I>Andrew Tridgell</I><BR><I>1998-11-09</I></ADDRESS></BODY></HTML>
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<H1 ALIGN="CENTER">The rsync algorithm</H1>
<P ALIGN="CENTER"><STRONG>Andrew Tridgell Paul Mackerras
<BR>
Department of Computer Science <BR>
Australian National University <BR>
Canberra, ACT 0200, Australia</STRONG></P>
<P ALIGN="LEFT"></P>
<P>
<H3>Abstract:</H3>
<DIV>
This report presents an algorithm for updating a file on one machine
to be identical to a file on another machine. We assume that the
two machines are connected by a low-bandwidth high-latency
bi-directional communications link. The algorithm identifies parts
of the source file which are identical to some part of the
destination file, and only sends those parts which cannot be matched
in this way. Effectively, the algorithm computes a set of
differences without having both files on the same machine. The
algorithm works best when the files are similar, but will also
function correctly and reasonably efficiently when the files are
quite different.
</DIV>
<P>
<P>
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<!--Table of Child-Links-->
<A NAME="CHILD_LINKS"> </A>
<UL>
<LI><A NAME="tex2html6"
HREF="node1.html">The problem</A>
<LI><A NAME="tex2html7"
HREF="node2.html">The rsync algorithm</A>
<LI><A NAME="tex2html8"
HREF="node3.html">Rolling checksum</A>
<LI><A NAME="tex2html9"
HREF="node4.html">Checksum searching</A>
<LI><A NAME="tex2html10"
HREF="node5.html">Pipelining</A>
<LI><A NAME="tex2html11"
HREF="node6.html">Results</A>
<LI><A NAME="tex2html12"
HREF="node7.html">Availability</A>
<LI><A NAME="tex2html13"
HREF="node8.html">About this document ... </A>
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<ADDRESS>
<I>Andrew Tridgell</I>
<BR><I>1998-11-09</I>
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