the load on the server at a particular time depends on the number of concurrent users. Not on the total number of user accounts and not on the number of users logged-in
The term "concurrent users" is used to mean those users for whom the server is actively doing something
The worst possible scenario is a large class all starting a timed quiz at exactly the same time. Luckily, users sat reading stuff are not generating any server load at all (until they click for the next activity/page). Very roughly, worst case, your Moodle site may only handle as few as 10-20 concurrent users per GB of memory. Moodle is a large application and can easily use more that 50MB (sometimes a lot more) of RAM per process.
What is the easiest way to increase performance?
Buy more memory!
My site is very slow, what should I do?
First find out "how slow". (The theme-trick here).
The next question is, whether the performance is normal or something malfunctions. There are many things which can malfunction:
- hardware
- crashed filesystems, specially network filesystems
- memory leaks or other crashes in the system
- bug in Moodle
- corrupted database
- networking issues (DNS, firewalls, ...)
Or your performance could be "normal" under the given circumstances:
- Are you on a dedicated server or a shared (virtual) server?
- How much RAM, processing power do you have?
- What is the software stack you use? (Unix or Windows, Apache or IIS, MySQL, PostgreSQL or SQL-Server, ...?)
- how many concurrent users can you support
- what modules/activities you use? Check Performance recommendations#Performance of different Moodle modules
Performance recommendations#Obtain a baseline benchmark and compare it with the published figures.
What is the best webserver?
It depends who you ask. Apache is almost universal on Unix and Linux. but Nginx is out performing latest Apache versions and gaining momentum for the last couple of years. IIS is native to Windows Server but Apache can be used as well. As always, the latest version available is likely to provide the best performance. There are other "niche" web servers. If you are interested in one of those you are likely to know about it already.
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