Currently yum-presto only reduce the update data. yum-presto should reduce the metadata of rpm as well. Afaik, it was on yum-presto's roadmap, to reduce the size of the metadata using deltas. And according to this comment [1] developer hasn’t had the time to implement this feature yet. I guess, someone might help him with some patches? [1] http://angelinux.net/2011/10/my-dilemma-with-yum/#comment-55
We already have this covered in a much earlier bug report. And yes, I would greatly appreciate any patches. *** This bug has been marked as a duplicate of bug 529358 ***