Re: metalink and debian mirrors ? (was: where to sync from?)
On 3/27/07, Simon Paillard <simon.paillard@resel.enst-bretagne.fr> wrote:
On Fri, Mar 23, 2007 at 01:55:54PM -0400, Anthony Bryan wrote:
> > Actually, there is a solution :) I'm involved in a project called
> > metalink (some of you may heard about it) which is targeted to file
> > downloads.
> > The purpose of metalink is to allow users to download a file from
> > multiple locations (eventually using multiple threads). Reading this
> > thread, I'm thinking that metalink can be used to implement simultaneous
> > downloads from multiple mirrors at the same time.
I remember this discussion you were part of :
http://lists.debian.org/debian-devel/2006/09/msg01107.html
http://lists.debian.org/debian-devel/2006/09/threads.html#00012
Some more questions:
How does metalink handle the case of network topology/geography, i.e. is
it likely to load transit links unnecessarily ?
Do you mean, will it keep oceanic links from being used if more local
links are available? That is one benefit. It depends on the download
client and if it wants to use the location information available about
mirrors in the metalink.
Here's what that location and priority information looks like:
<url type="http" location="cl"
preference="10">http://ftp.cl.debian.org/debian-cd/3.1_r5/i386/iso-dvd/debian-31r5-i386-binary-1.iso</url>
Does it parallel d/l even if that is not necessary ?
That depends on the download client, although (in the metalink file)
you can turn segmented
downloads off, or limit the number of servers that are used, or the
connections to each server.
IMO, referencing several HTTP/FTP mirrors in a single metalink file
implies the same kind of issue as a round robin : a single faulty mirror
will impact the good working of the overall system.
I'm not sure what you mean, can you explain more?
A single faulty mirror (or many, as long as there is one good mirror
referenced in the metalink) should not impact the overall system any,
except of course that there are less servers available for the same
demand. The download clients will check automatically until they find
a good mirror. This is of course easier than the user checking
manually. One of the advantages of having this information in a
machine readable format.
--
(( Anthony Bryan
)) Metalink [ http://www.metalinker.org ]
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