Bug 183977

Description of problem:
Downloading large ISOs or a large number of RPMs to apply updates between
releases of the entire distro or individual packages can take a very long time
(with Rawhide updates in particular being the worst offender) and can be
discouraging for people who have bandwidth limits with ISPs (which is become a
lot more common as broadband speeds increase). SuSE Linux has, for a long time,
been using its "deltarpm" package to quite nicely solve this problem - the
binary differences are downloaded and applied to existing RPMs or ISOs and the
whole updating process is significantly quicker than Red Hat/Fedora's.

Version-Release number of selected component (if applicable):
deltarpm, written by SuSE, is currently at version 3.3.

How reproducible:
Every time.

Steps to Reproduce:
1. Just track Rawhide in your yum configuration and then don't do any updates
for a week. Or...
2, Download and install, say, the Fedora Core 4 ISOs and then run "yum update"
(i.e. many months after the distro media release).

  
Actual results:
In both cases, updates can run in into the hundreds of MBs and take many hours
if you don't have a fast very broadband connection.

Expected results:
You should be able to download the binary differences and reduce the
bandwidth/time needed to update software.

Additional info:
SuSE not only use deltarpms as part of its YaST Online Update, but it also
supplies delta ISOs (if they save enough space - sometimes they skip them if
there's been a big package reorg) to allow you to go between, say, Beta N and
Beta N+1 versions of their distro. Example - I'm downloading the delta ISOs for
Beta 5 -> Beta 6 of SuSE 10.1 - it's a 167MB download, which I can achieve in a
few hours. If I want to get Beta 6 from scratch (which I had to do for Fedora
Core 5 Test 3 recently for example), we're talking about a 3GB+ download and
probably a few days.

Personally, I'd start with just delta RPMs for Rawhide and only keep a single
set of deltas (i.e. between the previous version and the current version of each
package) - you may also want to not provide deltas if they're too big (e.g. more
than 50% the size of the full latest RPM). Obviously, yum would need modifying
to able to look for delta RPMs and fallback to the full RPM if one wasn't
available. After that, I'd expand it to the normal update repositories, but this
time keeping up to 2 deltas - one like Rawhide (between previous and current
version) and one to go from the base install media version and the current
version - this would cover 99% of delta updates people would require. Finally,
I'd expand the concept to match the delta ISOs that SuSE provide, but keep this
strictly as deltas between test release ISOs only (6-8 months elapse between
full releases, which would mean the delta would probably be too big).

Further URLs for reading:
http://en.opensuse.org/Download_Help - explains how SuSE users can apply delta ISOs.
http://dag.wieers.com/packages/deltarpm/ - yes, good old Dag provides Red
Hat/Fedora RPMs for deltarpm, but it's all a bit sad that RH/FC don't use them!