I'm writing this after about 3 days of researches without ending in a solution that has sense.
I had several setups to host Wordpress sites, using Apache directly and using Plesk, everything hosted on AWS. Recently I setup a new Plesk installation on a m5a.xlarge instance, and things started behaving strange.
Basically the performances on this new instances, profiling the TTFB of the wp-login.php are unacceptable. We are talking about 2.0 secs in comparison of the old setup.
To make the thing short, I made tons of tests and the results are the following:
- TTFB 0.3-0.4 on Apache AWS Linux 2 with Mariadb 10.2, t3.medium
- TTGB 0.3-0.4 on Plesk t3.medium running Mariadb 5.5
- TTGB 1.8-2.2 on Plesk m5a.xlarge running Mariabdb 10.5 (the last one).
- Final test, bring up a new machine m5a.xlarge and installed another plesk, TTFB 0.2-0.5 but plesk installed Mariadb 5.5
Now first of all I did not understand why plesk intalled 5.5 twice and 10.4 on one instance. There's no choice during the installation.
I made every kind of test, I have the sensation that there's something about encoding and collations, but also running a mysql benchmark from withing WP, no differences are shown and the results are pretty much the same.
So anyone can show the light what's going one there ? Mariadb 10.5 ? Or is it possibile a faulty disk ? Ever happened ? (I also detached the disk and tried on another instance, no difference, so faulty instance is out of scope).
Thanks !