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Re: Yum-presto 0.3.9 - FC6 *and* Rawhide



On 4/16/07, Jonathan Dieter <jdieter gmail com> wrote:
Someone else asked about the format of the diff, etc.  Deltarpms can be
combined quite easily. For example you might have a deltarpm for
foo-1.0=>1.1 and a deltarpm for foo-1.1=>1.2.  You can combine the two
into foo-1.0=>1.2 and it will be roughly the same size as if you ran
makedeltarpm foo-1.0 foo-1.2.  This means that we don't *have* to keep
old rpms around to create deltarpms.  We just have to have the latest
rpm for each package + old drpms.

I will write whatever needs to be written to make pruning work, etc.
I'm just not quite there yet.

That is great that the diffs can be combined in this way. It allows a
lot of flexibility in how the source lays out the diffs for the
mirrors to clone.

I guess my point, now that I know that presto is able to do this,
would be that while the result of a merging of two incremental diffs
won't be much different in size than doing the diffs directly, the
keeping the two diffs separate themselves will be much larger than a
single diff bridging the same version gap; especially if the package
changes are done to the same files repeatedly.

So I guess the trade-off has to be made as to whether you keep around
a lot of diffs and use up some storage space just to accommodate
giving some efficiency to those who don't update frequently. Thomas
suggests 14 days. I would be more inclined to give a month. In the
end, if worse comes to worse, people just end up downloading the full
version of the rpm so it is not the end of the world.

Maybe there are some stats available from the various yum repo
maintainers as to when requests for specific package updates drop off
for those packages not superseded by another update.

/Mike


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