Not sure if it's the largest but we develop and maintain a website for AIESEC which is an international student organization with members in more than 80 countries.
Some facts about http://www.aiesec.net
- OACS 4.6.3 and .LRN 1.0
- >120,000 registered users, about 50,000 are active
- more than 20,000 users logged in within the last 24h
- so far easily up to around 100 concurrent users
- 1 load balancer
- 2 web server (Single 2,8 GHz P4-Xeon MT, 2 GB RAM)
- 1 database server (Dual-Opteron 242, 1,6 GHz, 4 GB RAM)
Until very recently, we only had one webserver (Dual-P3 933 MHz, 2 GB RAM) which would support up to 60 concurrent users but after that become quite unstable. The portal system of .LRN 1.0 is very resource-intensive.
