Hardware and performance

Not really - I was suggesting that anything you find with 8GB of RAM in it probably comes with a 4-core processor (say) by 'default'.

I was more suggesting that, load wise, a server of this nature will be spending a lot of time waiting for the disk. You rarely see constantly high processor load. However, as usual, in the real world it depends on what you are doing.

I suspect what you are looking at is a 2-core processor graph. It's a slightly mathematically challenged 100% per core.

Look at Load Average too, although you might want to read up on exactly what that means.

Exactly, a server can't be at 200% load, so if you generate that much load, your server will crash, and that is a bad thing

One tip I have heard recently from a couple of sources is is that PHP-FPM (http://php.net/manual/en/install.fpm.php ) is better for high-performance Moodle sites. (One source was the Catalyst IT talk at the Dublin Moot, another was the OU server folks.) We have not tried it yet for the OU Moodle, but it is on our list to do some load-testing.

There is a module for moodle a few of us have hacked away at that can help you generate a load testing script. You can get it from https://github.com/lucisgit/moodle-jmeter-script-generator .

With that you can get it generate a script that will go through your quiz. You need a thing called jmeter to run the script. You can use the jmeter gui (Or just change the script in a text editor) to alter the parameters of the test. The amount of threads to use (Ie. individual users) and the delay between page loads are the two main variables to alter to come up with a reasonable simululation of what you think is going to happen in the real world.

And you have can have 200% load, sometimes it is represented that way. 'top' does this if a machine has multiple cores, so with 8 cores you could possibly see 800% load.

The architecture of how you've setup your moodle installation can alter how many reasources you will need to give it.

No not at all!! Look at how much was actually used.

For the web server at 60 students, 6.5-7 gbs of ram would suffice, you get away with lower but then your "Next" clicks for each question would increase to 3-4 seconds which some students get annoyed about in a timed test.

MySQL Server InnoDB Pool Size needs to be at least 4gbs so your system would need at least 6gbs of RAM in a 2 server scenario.

In a 1 server scenario you can probably get away with 8-10Gbs of RAM and with todays modern processors really any would do, most are 4-6 core would suffice. In a virtual environment like ours we gave it 1 processor with  4 cores. Our processing power rarely goes over 10% with less than 100 students testing. When we get over 100 it gets used a little more, memory mainly!

The specs I mention above would give you around a 1-2 second delay between clicking to the next question. Average around 1 second, which is good. Must use a PHP Accelerator also.

I highly recommend a dedicated server! DO NOT use a VPS or shared unless you are going to get a garunteed or reserved amount of IOPS. Your neighbors on the shared system might be using all available IOPS killing your Moodle site. Very important for MySQL