Hardware and performance

Karmali, for this large installation, ideally you must have a separate box for database, fastest PHP Handlers as I am aware of on Apache are mod_php (Apache's own) and FastCGI, where FastCGI has added benefit of security like suPHP does, but at the cost of highest memory usage in all PHP handelers, at the same time lower CPU usage as compared to suPHP , but as you are already on 128G's, so shouldn't be an issue with you, also so far only FastCGI can support PHP accelerators like APC, OpCache etc, and speaking of OpCache, it does brings LOTS of performance improvements.

if it would have a windows server, i would have been in better position to assist you, Wondering why no one has replied where 95% of the community is Linux driven.

Might want to read this blog:

https://www.chriswiegman.com/2011/10/fastcgi-vs-suphp-vs-cgi-vs-mod_php-dso/

"best comparison"?   Will leave that to others to comment upon but it does explain some things.

One of 'catch22's' for folks who are on shared systems is suPHP.   After reading the above blog post, me thinks for your implementation, suPHP will just get in the way.

Think someone mentoned in a another posting some where in these forums, about Linux distro's not having PHP 7 (reportedly better than previous versions) it doesn't mean one can use other repos that are reputable 3rd party providers of packages not yet offered by the distro.    CentOS is of the RedHat 'family' and mimics RedHat Enterprise (without the RH eye candy and RH repos).   RedHat has been traditionally 'conservative' and slow to provide upgrades to 'latest and greatest'.   This is because, I think, they put stability over 'latest and greatest'.   CentOS will require reputable 3 rd party repos for some things ... like PHP.   Until RH and thus CentOS and the rest of the RH family 'moves upwards'.

Too bad there aren't more K12 people in here ... 6000 a month is close to what some K12 implementation of a Moodle would do in a day.   K12 with 'bring your own device' + 1:1 (students issued laptops/tablets to use just like textbooks) and that has a Moodle, that Moodle will get used ... period.   Most courses in  such a Moodle are either blended or 'flipped' and those approaches do make a difference on usage of Moodle and when thus a k12 Moodle will get more hits in a day than implementations for a corp or even some higher eds - those are asynchronous ... not synchronous.

So some of the decision about what and how much needs to be base on projected use.   Better understanding of how it will be used leads to better decision making.

My 2 cents ... of course!

'spirit of sharing', Ken

Opcache is used for storing compiled PHP scripts and storing them in memory, thus saving disk and compiling operations. Definitely worth having and I find using a monitor helps to understand what's happening, see http://www.stevejenkins.com/blog/2014/07/my-favorite-zend-opcache-status-scripts/ for some examples.

memcached is used for storing variables and other data outputs into memory, rather than reading from the db or a file cache. Also worth having, though the default file cache is often just fine.

We're looking at using PHP7, and from my own tests we noticed a significant improvement in performance - don't have the numbers to hand, but it was about twice as fast.

That's the web side of things, then there's the database. As someone noted, it's worth having the db on a separate server. You're going to have to play with the settings for the DB to get the best config for your server and expected usage. It's a bit of trial and error.

With regards to reports, I think the OU operate a separate webserver especially for reports, something I'm considering doing at some point. This allows you to have slightly separate configurations like longer timeouts and more memory allocation to cope with the harder work, but without messing up everyone else.