On 04/30/2010 04:46 AM, Hedayat Vatankhah wrote: > Hi, > It would be nice if Jigdo downloads could be also provided so that > people with previous releases (e.g. Beta release) which have downloaded > (and cached) updates could easily create new installation media without > downloading much (which will be much less than delta isos). Jigdo/rsync/zsync all have roughly the same efficiency (ignoring the large template file which must initially be downloaded when using jigdo) in that they avoid downloading unchanged packages, but updated packages must be downloaded in full. Deltaisos also avoid downloading unchanged packages, but in addition save space for updated packages by using deltarpms instead of full RPMs. So a deltaiso between 2 given ISOs should always be more efficient (in terms of size) than any of the others in doing the conversion. Of course this is assuming that a single deltaiso between the two ISOs is available (as opposed to having to use several to go from A to B, then from B to C, etc. which is much less efficient). It's not feasible to produce a deltaiso between every pair of ISOs since the number grows quadratically. However, most testers download each TC/RC, so deltaisos just between successive TCs/RCs are usually enough. On the other hand, using deltarpms is expensive in terms of CPU. The tradeoffs between downloading deltarpms vs. full RPMs are exactly the same for using deltaisos vs. jigdo/rsync/zsync as they are for using yum-presto vs. not using it, so anyone who currently finds yum-presto of benefit should be better off using deltaisos vs. any of the other choices (even if they were available).
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