Jigdo - A Professional Letter to Mike McGrath

John Poelstra poelstra at redhat.com
Thu Dec 6 21:38:12 UTC 2007

Jonathan Steffan said the following on 12/06/2007 01:28 PM Pacific Time:
> Hash: SHA1
> Ah, what a wonderful scholastic assignment. It's also great that Mike
> is going to have to open the letter once it actually makes to him.
> Dear Mr. McGrath,
> As long time Fedora developers, we both have watched and lived through
> the growing pains of Fedora releases. With the onset of the merging
> between core and extras, we have successfully created the needed
> infrastructure on which even basic Linux users can create their own
> Fedora-based derivative distribution. Along with this achievement comes
> the task of providing hosting infrastructure for an average
> user/developer to be able to share his/her creation with the world. An
> additional benefit in being directly involved in the sharing of the
> "Spins" is the ability to data mine what packages people are including
> in custom spins as to give our developer base more focus. To be able to
> fulfill this task, please consider requesting additional resources to
> archive signed updates so that they can be publicly accessed for the
> duration of a release life-cycle.
> The long road of Fedora development has been bumpy and even not
> enjoyable at times. Throughout the duration of the Fedora 7 release, we
> have made some very amazing changes that helped to open Fedora up to
> the masses. One of the most community-based features is the ability to
> Re-Mix and Re-Spin the distribution as the end-user sees fit. Being the
> server team lead for Fedora Unity, I've had to come up with unique ways
> to share the Re-Spins we compose. After trying many approaches with
> different technologies, we have settled on using Jigdo, the jigsaw
> downloader. Debian has used Jigdo for some time now and after poking
> their system for a while I've seen they keep every update they push. I
> do understand that Debian is considered a stable distribution much in
> the way RHEL is considered stable. This makes the updates tree not as
> active and it is easier to find mirrors to carry the full data set for
> an extended period of time. We, however, need to find a way to offer
> this same extended life for signed packages that have hit the Fedora
> updates tree.
> 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.
> The current updates system is getting better each release, but I think
> we should adjust our policies to also have an “updates-archive”
> repository. This repository will include all signed updates that had
> once lived in the updates repo, for the duration of the releases
> life-cycle. I don't expect all mirrors would want to carry this extra
> data so making the new repo optional will be a must. With the new
> MirrorManager, we will be able to effectively point users at mirrors
> that have been willing to take on the extra footprint. These requests
> to MirrorManager could be used to compose reports on what packages the
> community is utilizing most, allowing us to better focus our efforts.
> By providing an unified point of entry for data, we will be able to
> also log requests for package data found on in-house and non-official
> spins. By utilizing the abilities of MirrorManager to return specific
> mirrors for pre-defined IP blocks, we will enable end-users and
> companies to download from on-site mirrors while maintaining complete
> transparency. I hope that with advancements in Jigdo client software we
> will be able to look at using Jigdo to host our official images. Please
> let me know your thoughts on this matter. 

Hasn't the door already been opened for this?

Also, I see an incomplete feature page here: 


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