http://en.wikipedia.org/wiki/Wikipedia:Job_queue

Job Queue is running mostly for caching the pages and revalidating cache. Cache can go invalid, if page is added, deleted etc. The links have to change colors (red - does not exists, blue - does exist). 500 operation per job are done.

Wikipedia never reaches zero jobRates, as there are so many edits and visits?

WikiMedia server overview:
http://upload.wikimedia.org/wikipedia/commons/d/d8/Wikimedia-servers-2010-12-28.svg

Wikipedia hardware cost until 2007:
Total cost USD: $1,180,000

Peak load around 50 000 requests per second
CPUs total: 3424 (Avg load: 27)
Squid CPUs: 8 (Avg load: 72)
Apache CPUs: 848 (Avg load: 62)
SQL CPUs: 340 (Avg load: 22)


Wikimedia servers current status:
http://ganglia.wikimedia.org/
