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Re: Announcing Fedora Activity Day - Fedora Development Cycle 2009



Michael Cronenworth wrote:
Matthew Woehlke wrote:
What about dropping hierarchical mirroring altogether? Why hasn't
someone developed a distributed (i.e. bittorrent-like) system for mass
mirroring? :-)


Already discussed[1][2] on the fedora-test-list.

[1] https://www.redhat.com/archives/fedora-test-list/2009-June/msg00032.html
[2] https://www.redhat.com/archives/fedora-test-list/2009-June/msg00062.html

It's too bad fedora-test-list doesn't seem to be on gmane (or isn't named obviously; gmane.org is being too slow for me to ask about the mail address).

In an idealized network (all servers have roughly the same speed links to all other servers), BT distribution should get everything to everyone in about 2x as long as to send everything to one server. In the worst case, it should take 2x as long as to send everything over the slowest link in the mesh, which if only care about when /all/ mirrors are fully synced (a very reasonable assumption in this type of scenario) is still pretty close to being an unconditional improvement. In practice, the actual result will be somewhere between 2x the time to transfer over the fastest link, and over the slowest link.

In a generalized sense, the time-order to distribute via bittorrent in an idealized network is O(2 * K), where hierarchical systems are, at best I believe O(log(base N) K) for the furthest mirrors, and still O(N0 * K) for the tier-0 mirrors. That's an improvement of an entire order (O(log n) -> O(n)).

The point about there not being tools currently is what would need to be addressed.

--
Matthew
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