Jigdo - A Professional Letter to Mike McGrath

Mike McGrath mmcgrath at redhat.com
Fri Dec 7 15:18:12 UTC 2007

Jeroen van Meeuwen wrote:
> Mike McGrath wrote:
>> Jonathan Steffan wrote:
>>> The amount of storage and bandwidth able to be saved can be illustrated
>>> by a simple comparison between the efficiency of chopping up a 3.4GB
>>> iso9660 file system arbitrarily (by a static chunk size) and the same
>>> file system based on contents (file by file.) For a BitTorrent,
>>> Fedora's current choice for sharing Spins, the hosted data is only
>>> valid for a given chunk on a single ISO. This data's footprint (equal
>>> to the combined chunk sizes of the entire torrent) can be used for
>>> nothing but this Spin. To be able to host 5 Spins composed from similar
>>> trees via BitTorrent, we now have a footprint of 17GB, not to mention
>>> "seeders" have to run BitTorrent software to be able to contribute to
>>> the swarm. Alternatively, Jigdo can be used to reduce the footprint of
>>> these 5 Spins to about 4GB. The amount of additional data needing to be
>>> hosted for each Spin, in addition to what data is already pushed to the
>>> mirrors, is about 150MB per ISO with anaconda and about 200KB for ISOs
>>> without the installer bits. To help illustrate the efficiency of using
>>> Jigdo vs BitTorrent, the footprint for 250 Spins is 850GB for
>>> BitTorrent and about 40GB for Jigdo. Additionally, a reduction in
>>> overhead can be achieved by removing the need for the BitTorrent
>>> tracker and all related network traffic without requiring any
>>> additional work on the part of mirror administrators.
>> My concern with jigdo is with how many people use it?  It seems silly 
>> to host both torrent and jigdo (as much of this letter points out the 
>> benefits of switching to jigdo, those benefits disappear if we simply 
>> add jigdo to the mix.  Most people already have bittorrent.  Lets say 
>> we were going to give Jigdo a trial run for Fedora 9
> FYI, we have done so, and we are doing so officially for Fedora 9.
>  and we were going to
>> judge jigdo a success if a certain % (compared to bittorrent) use 
>> jigdo.  What % would that be?
> Jigdo would in this case be particularly useful to those with a local 
> mirror as they have 99% of the content already (90% if you have 
> F9T3?). Because it is particularly useful to some, and completely 
> weird and strange for others, the number of users that will use it if 
> BitTorrent is an alternative wouldn't be a very good indicator to see 
> if it is actually a viable distribution method for the whole of 
> Fedora, neither is it the goal for these proposals.

I'm talking specifically about people going to the get-fedora page and 
clicking on the torrent link vs the jigdo link.  Out of every 100 
people, how many people will click on the jigdo link?


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