[announce] yum: parallel downloading

[Reindl Harald]

Am 18.05.2012 20:31, schrieb John Reiser:
> On 05/18/2012 08:59 AM, Reindl Harald wrote:
>> why are making the connections to the SAME mirror at all?
>> it would make much more sense to download packages
>> parallel and each one from a different mirror
> 
> I find that two simultaneous threads to the same one mirror
> gives shortest time to completion for an entire list of downloads,
> particularly when one thread downloads from smallest to largest,
> while the other thread downloads from largest to smallest.
> The latency for setup+takedown of a connection for each package
> represents lost bytes that could have been transferred.  The other
> thread fills that gap much of the time.  When both threads actually
> are sending, then the network algorithms (and/or server policies
> regarding allocation of resources to the same endpoint) work,
> maintaining near-maximal total transfer rate at very low cost.

this doe snot help well if the mirror does not offer more
than 1 MB/sec while my connection can 12 MB/sec

i saw this last week by a KDE update of a co-wroker
download creeping around, CTRL+C one time picks
a mirror which is not really faster and the second
CTRL+C stops yum :-(

is such caes you have > 20 packages with > 1 MB and
could by using a different mirror for each one really
use the 12 MB/sec download rate of the client

with more than one connection you finally only abuse
overloaded servers more and make things worser

in 7 years fedora i saw only one time a dist-upgrade with
10 MB/seconds with yum (in times where each CTRL+C switched
to the next mirror instead stop the download)

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