Disk writing increase after upgrade from openSuse 42.3 to 15.0


I have a problem with the dis load since I upgraded from openSUSE Leap 42.3 to 15.0.
As for every upgrade I basically stopped the main services, changed the repos and run zypper dup. After restart and starting everything again everything seemed to work. But then I recognize in the monitoring an increase in the IO writing statics on the system disk (btrf file system). This also leads to a noticeable decrease of system performance and leading the system to be a significant portion of time in iowait.

This is what I found out so far:

  • The source of the problem seems to be the nextcloud instance running in docker. It contains of a nextcloud 15 container, mariadb 10.3 container and redis 5.0 container. When I stop these, everything goes back to normal.
  • These were exactly the same containers in the beginning as before the upgrade. Of cause during the analysis I recreated the containers, but this didn’t change anything.
  • Docker version is the same in openSUSE Leap 42.3 and 15.0 according to the package list.
  • When I make sure, that no request can reach the nextcloud and I deactivate the cron job calling it every 15 min, then there is NO increased writing on the disk.
  • Because the effect is intermitting, it is hard to tell what exactly is causing it, but looking at iotop for a while it seems to be the mysql database causing the increased writing. But what should have changed here compared to before the upgrade.
  • I cannot find anything unusual in the logging of nextcloud or mysql, no problems or errors reported.

I am running out of ideas, not really sure if it is a nextcloud issue or more operation system. So every hint would be highly appreciated. What would be further directions to head?