Slow Moodle 3.8.2 with Galera cluster - cache configuration?

Slow Moodle 3.8.2 with Galera cluster - cache configuration?

by Monica LOUPOT -
Number of replies: 1

Hello,

I installed the 3.8.2 version for our Moodle.

It has been tested on Development and Preproduction servers and I did not notice any performance issue.

On the other hand, in production we have a different infrastructure consisting of a Galera cluster with 3 nodes and the Moodle is very slow (see in attachment the results of our benchmark plugin).

I don't manage the configuration of the Galera cluster, but I could ask the dedicated team for more information if you think that there are adjustments to be made on their side.

In the meantime, digging through the Moodle forums, I have configured the cache (see attached screenshot for data warehouses) and below:

    APCu cache for:
        Accumulated information about modules and sections for each course
        HTML Purifier - cleaned content
        Language string cache
        List of available languages
    Memcached for:
        Activity completion status
        Calendar subscriptions
        Concept linking
        Config settings
        Course categories tree
        Course group information    
        Database meta information
        Event observers
        Grade items cached for evaluating conditional availability
        Plugin info manager
        Plugins available callbacks
        Question definitions
        System capabilities list
        This stores the list of event subscriptions for individual courses
        User grades cached for evaluating conditional availability
        YUI Module definitions
    For the rest it is either "Default static store for request caches" or "Default file store for application caches" or "Default session store for session caches".

Does this configuration seem correct to you?

Thank you in advance for your advice and help.

Kind regards,
Monica

Attachment benchmark_moodle2020.JPG
Attachment cache_config_moodle2020.JPG
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In reply to Monica LOUPOT

Re: Slow Moodle 3.8.2 with Galera cluster - cache configuration?

by Visvanath Ratnaweera -
Picture of Particularly helpful Moodlers Picture of Translators

No. Moodle sees a very slow file system behind its $CFG->dataroot, what we just call "moodledata". The Moodle Bench reports:

 3 Reading file performance
(Read a file multiple times to check the reading speed of the Moodle temporary folder)
current 0.567 acceptable. 0.5
4 Writing file performance
(Write a file multiple times to check the writing speed of the Moodle temporary folder)
current 5.6 acceptable 1.0

Notice that the numbers are in seconds - smaller numbers are better.They have to be clearly better than the acceptable limits. Specially the write speed, completely unusable.

What was the Moodle Bench score? It is left out in your screen-shot.

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