Jigdo - A Professional Letter to Mike McGrath

Mike McGrath mmcgrath at redhat.com
Fri Dec 7 14:48:10 UTC 2007

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 and we were going to 
judge jigdo a success if a certain % (compared to bittorrent) use 
jigdo.  What % would that be?

While google trends is sort of crazy in that I don't know what it says, 
it does say something:



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