Jeroen van Meeuwen from our Spins SIG was kind enough to send me this information on Jigdo:

“The jigdo method of distribution basically works as follows: for every file in a .iso that you tell jigdo is available from somewhere else, it strips the file (or slice, or piece of the .iso jigsaw) from the .iso leaving you with a relatively small .iso.template (only the parts of the .iso that are not available from somewhere else) and a list of files you can get from somewhere else.

“Now, with installation media, this means there’s a small part of the .iso you need to download in the form of a .iso.template, while the rest (install.img, and all RPMs) is available from any mirror (and you are going to use the closest and fastest one).

“With Live media however, the contents of the .iso is just a few files. Some of them are really small (vmlinuz0, initrd0.img), while others are very large and make up 99% of the size of the .iso (osmin.img and squashfs.img). Splitting those slices from the .iso isn’t very useful, because you would end up downloading a small .iso.template, several very small files, and then one single beast of a file (squashfs.img).”

Hopefully this helps clarify our jigdo availability. Thanks for the question!