On 12 March 2010 14:08, Patrick O'Callaghan <pocallaghan@xxxxxxxxx> wrote:
The yum fastestmirror plugin (yum-plugin-fastestmirror) claims to
evaluate the speed of a bunch of repo mirrors and use the fastest one
relative to the user's location.
However AFAIK what it *actually* does is make a test connection to the
to the candidate mirrors and order them according to response time,
which in many cases is dominated by network latency, which can distort
the results. For well-connected user machines in first-world countries
it probably doesn't matter much, and may have the beneficial effect of
spreading the load over a wider range of mirrors, but for those of us in
a less privileged position it can matter a lot. Ironically, these are
the cases where such an optimization could do the most good.
A case in point: I live in Venezuela and on several recent occasions yum
decided that my closest repo was in Puerto Rico, which as the packet
flies is probably true. However the b/w I got as a result was around 2
or 3kbps.
I tried renewing the mirror cache. No difference (ping times tend not to
vary much).
I then manually edited the /var/cache/yum/timedhosts.txt file to bias
the results against the mirror yum was choosing (I made it worst rather
than best). Oddly, it again made no difference! It seems there's a
cunning hidden cache of these results that I don't know about. Finally I
disabled the plugin completely and got decent b/w without it.
Perhaps we should be considering some kind of BitTorrent version of the
repos in which the mirrors are seeds and the users are leeches, though I
realize that this is harder than it looks, particularly when taking into
account the synching of the mirrors themselves.
poc
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Perhaps not so difficult - though I've never used them myself, I recall that in the Debian, if not Ubuntu (Sometimes hard to tell) repositories are some packages that allow for bittorrent fetching of deb packages - perhaps if they're still relevent and working, they could be used as a base to create a means of implementing the same, maybe as a plugin for Yum or similar.
Theoretically, I think the only main differences are the download protocol. HTTP/FTP or BitTorrent. Once downloaded the package can still be used in the same way, there's no difference there.
The main downside I see to it is that those users on an ISP which throttles BitTorrent will suffer, and have to go back to standard downloads, but if both are provided, then no issue. Or at least very little.
Just my 2p. Or 2c, depending on your currency.
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