Dear Tim, I have followed your instructions in setting up the MUC with memcache. The result of the load test then becomes good. Thank you very much.
However, i still have the following questions which need your valuable advice:
1) When i setup memcache in the page "Cache configuration", i need to restart the web server after each change. And i need to modify the configuration file directly in order to set up memcache for session cache. Is it normal?
2) Will Moodle performance deteriorate significantly if one of the memcache servers is crashed?
3) What is the best way to purge Moodle caches? By performing "Development/Purge all caches"?
4) It seems there is improvement in the table locking issue (pls refer to https://moodle.org/mod/forum/discuss.php?d=221444) of mdl_cache_text in v2.4.4+ when there are many concurrent updates. Would you still recommend to set Text cache lifetime to No for large site with many concurrent updates as i want to achieve even more concurrent updates?
5) If i perform "Purge all caches" before performing the load test, the total number of hits would become smaller, say by 12% than the test without purging all caches. Is it normal?
Thank you very much.