Issue Problems after migration to MariaDB

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Hello everybody,

I need to migrate the mysql server 5.5 that comes along with PLESK to mariaDB. So I searched across the internet and landed a hit here on the forums and blogs:

• Plesk 12 with Mariadb on Ubuntu 14.04
  https://talk.plesk.com/threads/plesk-12-with-mariadb-on-ubuntu-14-04.332680/
• MariaDB Installation Guide
  https://www.plesk.com/blog/mariadb-installation-guide/

I followed the "MariaDB Installation Guide" step by step and included the changed and additional steps from "Plesk 12 with Mariadb on Ubuntu 14.04". So far everything seemed ok. Just to make sure everything works fine, I did a system reboot. All services started without failure. I can access the PLESK web frontend and change settings, backup configurations, etc. The MariaDB database works and can be accessed from shell and from phpmyadmin. But since I switched to MariaDB the health monitor shows 100% cpu usage on mysql. When I lookup cpu usage from the shell via "top", cpu usage is normal.

Since the switch I am unable to receive emails. When I send an email from another mail account, the email seems to never arrive. I don't get any response like "unknown email address" or "server denies receipt". When I login from Horde I still can see my emails. I have received before I switched to MariaDB.

I just have noticed that the Update and Upgrade panel (domain.com:8447) is not reachable, even with firewall completely turned off.

I am unsure to run the repair tool since MariaDB did not originally come with PLESK.

Any ideas?

Best regards,
CB

Here is my setup:
Ubuntu 14.04 LTS (up to date)
PLESK 12.5.30 MU #56
psa-horde 5.2.6
postfix 2.11.0
PHP 5.6.29, 7.0.14
mariaDB 10.1 (stable)