> We've learned a lot in the past eight months since going with Moodle, but what we haven't learned is the proper setup for a large scale implementation of Moodle.
I was following the other thread http://moodle.org/mod/forum/discuss.php?d=159495
serving Moodle at this scale needs a lot of experience and know-how. Once you start "tuning" such installations, the whole thing becomes more of an art ;-(
Now to your questions:
> 1. What specific operating system would/do you use for a large scale implementation? (Fedora, Ubuntu, Centos, etc..) Also, which version of the OS?
Fedora, Ubuntu, Centos, etc. all are the same OS, Linux, a Unix-clone. They are just different "distributions" of Linux http://en.wikipedia.org/wiki/Linux_distribution
There are many other Unix-clones, very popular as server OS are the *BSDs: FreeBSD, OpenBSD, NetBSD, .. http://en.wikipedia.org/wiki/Comparison_of_BSD_operating_systems
Your question is which distribution, I guess. That is the second famous moot topic (behind the legendary Emacs vs Vi discussion). The neutral answer is, take the distribution you know well! For long answers, search this forum for "linux flavour".
> 2. Which version of PHP would you recommend in conjunction with the above OS?
Moodle dictates the minimam PHP version, and also a recommended version. If you know your distribution, you know how to get a particular version.
> 3. Which database management system (mysql
Somewhat similar to the distributions discussion. The people in this forum who maintain really big Moodle installations recommend PostgreSQL
. Again, this is a circular answer: If you know your database system, you know whether it'll handle the load or not, and how.
> 4. Do you virtualize your large scale installation?
I was surprised that you go with virualization for such a big installation. People here have repeatedy advices against (for big installations).
> 5. How much RAM should be allocated to handle the 1000 concurrent users in your experience in that large scale implementation?
says "The general rule of thumb is that Moodle can support 50 concurrent users for every 1GB of RAM, ..."
The whole thing sums up to years of experience, which can not be summerized into forum postings. Serving 8000 teachers and 75000 is not to be underestimated. Why don't you engage professionals who specializes on big Moodle installations for the job?