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Re: A more efficient up2date service using binary diffs



M A Young wrote:

On Fri, 11 Mar 2005, Jeff Johnson wrote:



This patch
   https://svn.uhulinux.hu/packages/dev/zlib/patches/02-rsync.patch
is in rpm-4.4.1 and on by default.

If the payloads in FC4 are not rsyncable right now, then it's because
beehive is using an
older version of rpm ... checking ... yep, current rpm payloads should
be rsync ready:

$ rpm -q --qf '%{rpmversion}\n' perl
4.4.1



It seems the option isn't active for FC3 and its updates (which is what I
had tested) so I have repeated the test with a couple of RPMs from
different rawhide mirrors using xdelta, which uses a similar algorithm to
rsync, and found the following sizes



Yep, rpm-4.4.1 is not in FC3, and so *.rpm payloads are not prepared with the zlib equiv of gzip --rsyncable.


libgcj-4.0.0-0.31.i386.rpm 13942525
libgcj-4.0.0-0.32.i386.rpm 13950302
xdelta of rpms              6911651
xdelta of header + cpio     3723074

thus there is a significent saving in size for small changes, though you
can do even better with more processing. Also from my experience with
openoffice rpm library rpms don't diff as well as other packages, so the
typical saving might be better than this example.


Hint: xdelta is the wrong approach, because both packages have to exist on either client or (more likely) server,
leading to a combinatorial complexity of deltas to manage for all possible updates.


Try rdiff from librsync instead.

73 de Jeff


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