We run nine schools in one Moodle system on one database. So we need only one server, one backupsystem.
Instead of categories we use the word locations, but the overview pages of Moodle become very overcrowded, so we have to find a solution for that:
There is (on this moment) no need to see the courses of the other locations from a user point of view.
What you can decide to do is run on one server and one database 3 different schools in separeted Moodles: the only thing you have to do is
- change for every school the prefix for the database in the config
$CFG->prefix = "mdl_";
- consider to give each school their own datadir (not necessary, but see at the end)
$CFG->dataroot = "....................\moodledata";
You then have three separated database sets in one database.
If you use email authentication - if you lock all the courses with a key then that is very secure - you are ready now. (We use one central LDAP, but I can imagine that schools find it hard to share taht...)
Start on each school Moodle with their own config....
You then can tune every school (even the themes) separated from the others, but still can live with one server and one brute force backup facility.
(Inside Moodle 1.3 you then can automate the creation of school specific backups, one for each school, sent to the location they prefer. Very handy when the want someday to setup their own servers...separate therefor the moodledata dirs..)