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Re: Debian 3.0 released. Jigdo files available.



On Tue, 2002-07-23 at 02:33, Georg Lehner wrote:

> If the download tool(s) could look at the local package cache or mirror
> if an older (not-too old?!?) version exist and rsync the newer version
> on top of bandwidth could be saved.  This is important at least for us
> with low (loooow) bandwidth capacities.  At times I have to recurse even
> to telefone links for my updates!

If the gzip used to compress the files inside the packages had been
patched to be rsync friendly, and if we were using that option, then
what you say might be true.  As it is, a one character change near the
start of a compressed file can (and normally does) result in two
compressed files with nothing in common that rsync could take advantage
of.

What makes this worse is that not only is using rsync in this manner
mostly pointless, but each connection inflicts significant load on the
server, so you end up doing a DDoS on our mirror servers.

There is a paper about this by Martin Pool (the new upstream rsync
maintainer):

  http://www.samba.org/cgi-bin/cvsweb/rsyncweb/rsync-and-debian/rsync-and-debian.sgml?rev=1.10&content-type=text/x-cvsweb-markup

in which he proposes that we switch to using rsync friendly gzip, and
that there be a modified version of rsync which reverses the algorithm,
and leaves most of the load on the client.  He also points out that this
could be done on most modern web servers, on the server side, with
either minor, or no modification.

It sounds a great idea to me, but it's not happened yet, so until it
does, doing this would be stunningly counter-productive, I'm afraid.

Cheers, Phil.

> 
> Of course this is not jigdo-functionality but debian-package and version
> administration functionality and maybe has to be handled "outside" of
> jigdo.
> 
> Best Regards,
> 
> 	Jorge-León
> 
> 
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-- 
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