This is Mr. Lau from Hong Kong. My institution is going to use Moodle 2.0.2+ as our production CMS platform. We have over 30000 users and 2000 courses. In http://moodle.org/stats/, we know that some universities have large number of courses and users in Moodle, e.g. over 100k courses and 50k users. They may run Moodle cluster and database cluster to cope with such high usage. In our environment, would you recommend me to use MySQL single instance or MySQL cluster or MS SQL server?
Besides, is it a must to use MySQL 5.0.25 for Moodle 2.0.2+? Can we use MySQL 5.0.77?
It always depends on your knowledge. Badly configured MySQL can behave worse than unconfigured MSSQL. I don't know anything about MSSQL, but if you want to depend on some technical solution, you'd better know something about it (:
If you choose MySQL don't even bother with 5.0. Use at least 5.1 or even 5.5.