Installing and upgrading help

Hi Danny,
MUC makes usage of three different scopes for caching: request, session, application. By default they are mapped using resources available in all the installations i.e. PHP static, PHP session, files within Moodle dataroot, under $CFG->cachedir.

That being said, if you have enough memory room (at least 128MB, it depends on the number of definitions being mapped) for a memory-based caching service you could install it and map:

a. one/all the default scopes to your caching service, e.g. request into your memcached instance;
b. a particular cache definition, e.g. core/string into your redis instance configured as drop-in replacement for memcached.

What required is:

1. a supported caching mechanism; please, consider even the so called memcached drop-in replacements;
2. the PHP support for that mechanism;.
3. select where to install the supported caching mechanism: it's common practice to install it on the front-end level, strictly closed to localhost.

Besides, starting from 2.2 there is an interesting option, $CFG->cachedir, to let administrators to configure the default caching file store within the context of the front-end, really useful when you deploy Moodle in a load balanced cluster environment; the same for $CFG->tempdir, see config-dist.php for details.
MUC almost requires to configure $CFG->cachedir within a local disk to each front-end, for default best perfomances or - MUC rocks! - to create a new file store instance mapped to a local folder and to map the application type to that local (to the n-th front-end) file store.

HTH,
Matteo

That MUC control panel is a bit like the big mixing desks you see in concert halls. It gives you lots of knobs to twiddle, but unless you know what you are doing, it is going to be difficult to get a good result.

Perhaps it is better to say "Until we, as a community of Moodle administrators, generate some experience it will be difficult to make good recommendations."

So, anyone who can measure their Moodle site while they try different things and report back about the effect is making a useful contribution.

Note that the default configuration for MUC mostly designed to be the equivalent of how Moodle 2.3 worked, so initially the performance characteristics are likely to be the same as you are familiar with. (Hopefully showing a small improvement already.)

The thing that a number of people have done in earlier versions on Moodle (by hacking the code) is to move the session storage out of of the database, and in to memcache. So if you want a good first thing to try, try moving the session caches to a memcache server.

If at all possible, please monitor your servers carefully before and after the change, to see what effect that has.

Can someone who knows about these things suggest a basic set fo things to measure?

As (is often the case) I had no idea what you were all talking about I did some digging. Moodle Universal Cache. Seems a bit light on documentation but I did find this...

http://docs.moodle.org/dev/User:Sam_Hemelryk/MUC_proposal

EDIT:
That sounded a bit rude. I mean *I* never know what's going on, rather than I don't know what you are talking about. Stop digging now