General developer forum

Perhaps one of the best people to discuss this with would be Tim Hunt. Tim comes from the Open University and I think thay have a much larger, perhaps the largest, enrollment base of any organization I know of.

Having said that, the issue you raise, that of multidisciplinary studies, is one of the more interesting phenomena in education in the last 20 odd years. It is certainly changing how Universities are operating, that is for sure.

Having had some experience with WebCT in a multi-campused organization, I can suggest the approach they took was not necessarily a good one. Each campus had its own WebCT install which also proved somewhat inconvenient when travelling between them not to mention the difficulties that seemed to magically appear when trying to move between disciplines, inside the same campus. (I think that was more about a lack of understanding of WebCT than it was the limitations of the program, but it may have been both.)

I noted then that the hardware also played a much greater role in the efficiency and stability of the program than I had thought. I am aware of a rather large organization curently using a commercial product updating its servers due to the poor performance of that product - but to be fair, there has also been an increase in the number of users which would also have an effect. Whether this will produce the desired results is somewhat questionable, I suspect, as I think the product deeply flawed due to the acquisition and incorporation of another LMS a few years ago that has not be properly digested, but that is another story.

As for Moodle, I do not think that you are going to get out of it cheaply. The hardware requirments alone are going to frighten you, with that number of enrollments - but I suspect that true of any LMS, and Moodle is one of the more efficient ones. A server cluster or farm that is mirroring or load balancing is going to be essential, I am sure you have already determined that.

However, one of the better setups I have seen was a cluster of ordinary PCs, used as servers. They used Linux, but what flavour I do not know, there was about 12 machines and the service was flawless. Admittedly, they were not dealing with 30,000 enrollments, but what I saw of it was pretty impressive. The techie said this was scalable to as many PCs they could fit into the room, but there would be a serious noise issue with the machine's cooling fans. They were doing on the cheap actually, and that system is still in use, btw, and still works well and it is much easier to replace a 350Eur PC than it is a 10,000Eur Server.

Hi Susana, at ~30,000 users the decision between a single instance or multiple instances really isn't about scalability, but about whether you are planning on having different modules, or plug-ins, different management policies, etc. on the different instances.

For scalability an essential metric you'll need to look at is peak load (also known as concurrency) - how many users may be on the site at one time. This is an especially important metric for academic institutions as peak load times tend to be around mid-term tests and finals, when you may have 1000s (or 10,000s) of students trying to complete online tests, submit assignments, check grades, etc. at the about the same time. Often system loads at these times are 2 times (or more) 'normal', this is also when system outages are most disruptive. So an essential part of designing a hardware solution for a large Moodle site is to design for the peak load times, and to build in a method of scaling the system rapidly, as well as recovering rapidly, from hardware or software failure, into your system plan. To do this, identify the points of failure and build in contingency.

Because Moodle has so many modules and can be used in many different ways, it's difficult to say 'build your system like this and it will work' - a site configuration (hardware and software tuning) that works great for a 30,000 user site where the courses use mostly resources and discussion forums will be inadequate for a similarly sized site where  there is heavy use of the quiz. For example one ~30,000 user site I know of has several courses with over 1000 students each - and these courses make heavy use of the Moodle quiz module for end of semester summat assessments, with randomized questions from very large question pools. Hardware requirements for this site basically double when students are taking these tests on the last day of the semester or if they happen to get scheduled at the same time during mid-terms. For this reason, it's essential to actively track your site's system resource usage throughout the year, discover when and what your peak loads are, and plan for them. Of course it's difficult to do this when starting 'from scratch' with no data.

At Remote-Learner, we currently have ~800 client Moodle sites, and many that are over 30,000 users. For most of the 30,000-40,000 user sites, our "level 4" configuration works fine (with some site specific configuration for peak load in some cases)- this is a highly tuned two box set up as described on our site. We have also implemented the Red Hat Enterprise Virtualization  server platform, which enables us to dynamically scale resources for peak load - we can dial up and dial down server resources depending on your needs, and often we'll start a 30k user site on a level 4 equivalent RHEV virtual server, and then work with  the client to tune the configuration to optimal performance.

Finally, for large sites, an essential component for adequate stability is well trained staff who can setup, monitor, and tune the system. If you are doing it yourself, a decent rule of thumb is 1 well trained SysAdmin for every 10,000 users (that rule is pretty much the same for users self hosting WebCT or Blackboard, by the way).

We also have our Enterprise Learning Intelligence Suite for Moodle - I only mention that because it has methods for mananging a multi-tenant Moodle system with one codebase, shared resources, etc. with the option for separate administrative structures for different organizations using the site - so for instance Department (or College) 1 can have a local admin who can manage & get reports on her/his own users without seeing the users of College 2. There is more information about that here if you are interested.

I wish you the best with your Moodle project!