On Sat, Jul 17, 2010 at 05:07:50PM +0200, Keld Simonsen wrote:
If not linear, how is the relationship then?
Eligible mirrors are looked up in the database with their prio, and then each mirror is ranked according to this little formula:
rank = (rand()>>16) * ((RAND_MAX>>16) / prio);
The mirror with the lowest rank is the one that's chosen. Thus, the choice is made by weighted randomization.
The probabilities of selection should be: 3 mirrors with prios 100, 100, 50: 41.7%, 41.7%, 16.7% 3 mirrors with prios 200, 100, 10: 73.5%, 24.4%, 2.1% 2 mirrors with prios 100, 50: 75.0%, 25.0% 2 mirrors with prios 500, 100: 90.0%, 10.0%
Anyway it looks like the novell site has been taken off the list for denmark.
It's not a Novell site as such - it's just a CNAME entry in the Novell DNS which points to Akamai's content server(s) (a CNAME itself, pointing to variable edge servers depending on your location).
This cname cdn.novell.com is handled like any other mirror in MirrorBrain, with the exception that it is not configured with a certain country, but with a wildcard, which matches all countries. Thus it's considered for requests from all countries. (For the files that it serves, namely those few ISOs.)
After the first release day, this special mirror is simply switched off in MirrorBrain, and from that point everything is redirected to the mirrors as normal.
And I read a little more about the cdn.novell.com site. I understand now that this is not a Suse site, but some other department in Novell. For a moment I thought that Novell was putting money into a Akamai site which was in fact just competing with their voluntary openSUSE mirrors, creating some worries about what was causing a drop down in the mirror traffic by seanoed mirror maintainers. But if it is another Novell project - well then all resources are well received, and of cause bandwidth always costs - be it donated by a university or a private firm.
To explain this: the bandwidth is surplus bandwidth that is available to Novell anyway (as a customer), and it donates this bandwidth to the openSUSE project. It's a nice gesture albeit it's of arguable use. I guess the motivation needs to be understood in a historic context; there was a time before openSUSE had a good download redirector.