ISO downloads with multiple mirrors for higher reliabilty, automatic checksum verification

Francois Petillon ftpmaint at proxad.net
Thu Nov 2 10:12:49 UTC 2006


Anthony L. Bryan wrote:
> I've made Metalinks for a few FreeBSD ISOs:
> http://www.metalinker.org/samples/FreeBSD_6_2-BETA3-amd64-bootonly_iso.metal
> ink

As these Metalinks are not officials, would it be possible to remove 
ftp.fr.freebsd.org from these files ? I do not want to support nor 
promote an "open standard" that encourage software to do parallel 
segmented downloads.

I have several problems with segmented downloads. As software open 
several connections (it may be several connections on a single server or 
single connections on several servers, the result is the same), servers 
will serve more connections and will have less memory usable per 
connection. As one of the biggest problem on servers is related to disks 
IO optimizations, less memory may lead to smaller block reads (and thus 
higher disk load). Even if the server has enough memory, as the file are 
requested by segments, you are disabling on the server the ability to 
fully optimize its disk requests. Last but not the least (and it does 
not concern bittorent downloads, only servers), if you do not download 
at max speed, it means there is a _real_ bottleneck. It may be on the 
server, it may be on the network but speeding up download by using 
segmented downloads will not create bandwidth, you will just steal 
bandwidth to other people.

François


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