Our configuration includes:
1. One Moodle Server - Dell PowerEdge 2850 w/ 2 Dual Core Xeon - 8GB memory - Red Hat EL 4 Moodle 1.8.2+,ELGG,eGroupware
2. One Database Server - Dell PowerEdge 2950 w/2 Dual Core 64 bit Xeon - 8 GB memory - Red Hat EL 5 MySQL 5.0.48
3. Three District LDAP Servers Dell PowerEdge 1850 - Novell
4. Two DNS Servers - Red Hat EL 4 - BIND 9.
Or first Moodle server is used primarily for staff development. It currently has 10288 users and 53 courses. The peak daily load now is between 1700 and 1900 users. The entire staff, all 10000+ just completed the Districts mandatory training. (I'm glad that is over)
We spent a great deal of time preparing test sessions for load testing our Moodle Site. We made a copy of a production course to test against. We had to turn off the facility of Moodle to jumble up the quiz questions. Otherwise our pre-recoreded user sessions would fail.
We used WebLOAD on 4 server PCs to test the system. The un-tuned server went belly-up early on. Then we began to peel the onion, so to speak, and uncover the layers of performance issues over the numerous iterations. The OS open file limit was increaesed. Apache and MySQL session timeouts were modified. Apache mem_cache was added. The MySQL key buffers and query cache were tweaked. Ethernet buffers were also increased.
We are in the process of deploying 3 more Moodle Servers. We are now piloting courses in 2 high schools. Soon Moodle will be available to every high school teacher in the district. But first we have to deploy an LDAP based registration server. The registration server will be deployed as a Xen virtual server running RHEL5 or Fedora 6 and the Fedora Directory. We will deploy a test Moodle server with Tux front end and Apache back end and repeat our perfomance tests. We will compare eAccelerator and XCache perfomance. If we can figure out how to configure lighthttp we might try that too. With school going on now, I doubt we will have any new performance metrics before the summer.