My Moodle site is run on an Ubuntu 10.04 x64 server with 2GB of RAM. It is Virtualized and runs on a VMWare ESXi 4.1.1 server. I have this on a home brewed OpenFiler iSCSI and for the longest time, this configuration worked without major flaws.
Over the Summer we upgraded our Moodle from 1.9 to 2.1 and now we have an issue with Apache and the memory usage. It seems like when we get a group of students on the server, it will spawn many apache2 instances, the memory usage goes up and then they don't seem to die off and release the memory.
I have tried editing the apache2 config to try to tweak it to what I found on the moodle.org site, but nothing seems to be helping.
It's odd that it didn't do this with the 1.9 version of Moodle with virtually the same setup.
I'm the wrong person to answer your question, I simply don't have any experience in VMWare ESXi technology. Since nobody answered I take a shot.
A fundamental question first. Why you have so much virtualization?
The fault could be in many places:
3. bug in Moodle 2.1 or
4. Moodle 2.1 requiring more ressources (indirectly virtualization)
From your description it sounds like 1. Apache. What is the exact version you have ($ /usr/sbin/apache2 -v) ? Can you simulate the memory leak with Apache Bench? (Request a static HTML page.) Are there reported memory leaks in your version? What was the version you had for Moodle 1.9?
The same story is valid for 2. PHP (/usr/bin/php). Are you sure you haven't upgraded your Ubuntu (apt-get upgrade) between 1.9 and 2.1?
For 3. You have to search the http://tracker.moodle.org
4. Moodle 2.1 generally consumes more ressources. It is possible that 2 GB were barely enough for your 1.9 but not for 2.1. You could try increasing RAM.
I did tweak my Apache settings and for now everything seems to be stable. I had some outragous, wacky settings in my Apache config. Trimming things down made a big difference.
Now it's on to troubleshoot other issues.
could you please post what settings you have now in Apache config ?
Would you be kind enough to share your settings? I have a server that's handing almost 4000 users also in a virtual environment, and I'm running into alot of crashing issues too.
I just upgraded to 2.1.2 in hopes that it'll help.