I have a serious problem on my new LEAP 15 that I never had on previous opensuse version and that I can't solve.

once or twice a day, at random time it seems, HDD start to work very hard and may be 20 seconds later, OS is not responsive anymore because of that. Mouse pointer is still alive and I can switch to console by alt+ctl+F1 but can't log for "delay is over" as the whole system is so slow.

I could run iotop as root on console "before" the bug start and noticed that almost all apps are hdd consuming : firefox, dolphin, soffice, akonadi, etc... Just like if at one time, all apps need to read an extraordinary amount of data on HDD ! iotop indicates that hdd is essentially "read", and very little "write".

I tried to let it run for half an hour but the problem stills. After hard reboot, everything goes well until next time...

I made jounalctl persistent but "journalctl --boot=-1" does not show particular matter at the date and time of the bug.
/var/log/messages does not give any clue either...

I unchecked the system search tool (baloo) but the bug still happens.

I'm not that familiar with archeology in the log files and I miss ideas to find out what happens and why...

If anyone could give me some magic shell commands or some log files to explore, that would be precious !

Thank for any help,