On Wed, Apr 10, 2002 at 10:25:22AM +1000, Martijn van Oosterhout wrote: > On Tue, Apr 09, 2002 at 05:02:34PM +0200, Michael Bramer wrote: > > you propose to add 'some' diff files for all files on ftp-master.d.o? > > > > With rsync we need only one rsync-checksum file per normal file and > > all apt's need only download the neededs parts. > > > > You get the point? > > With the standard rsync algorithm, the rsync checksum files would actually > be 8 times larger than the original file (you need to store the checksum > for each possible block in the file).
I don't see that the checksum file is larger than the origanl file. If the checksum file is larger, we will have more bytes to download... This was not the goal. > What you are suggesting is that the server store checksums for precalculated > blocks on the server. This would be 4 bytes per 1k in the original file or > so. The transaction proceeds as follows: > > 1. Client asks for checksum list off server > 2. Client calculates checksums for local file > 3. Client compares list of server with list of client > 4. Client downloads changed regions. Yes, this is the way.. > Note, this is not the rsync algorithm, but the one that is possibly > patented. maybe I don't understand the rsync algorithm... IMHO the rsync algorithm is: 1.) Computer beta splits file B in blocks. 2.) calculate two checksums a.) weak ``rolling'' 32-bit checksum b.) md5sum 3.) Computer B send this to computer A. 4.) Computer A search in file A for parts with the same checksums from file B 5.) Computer A request unmatch blocks from computer B and build the file B. I get this from /usr/share/doc/rsync/tech_report.tex.gz right? The _only_ difference is: precalculate the checksums on computer B Or maybe store the calculated checksums in a /var/cache/rsync/ cache dir. sorry, I know that partentes don't have any logic, but this is the same algorithm, only with some cache. Comments? Gruss Grisu -- Michael Bramer - a Debian Linux Developer http://www.debsupport.de PGP: finger [EMAIL PROTECTED] -- Linux Sysadmin -- Use Debian Linux "Nicht geschehene Taten ziehen oft einen erstaunlichen Mangel an Folgen nach sich." -- S.J. Lec
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