Hi there.

I recently added a cache disk to my array and created a "cache only" share on it for plex library data (them speeds).

Since then i get really high disk load for several hours.

It seems to be this line which starts the mayhem:

Here you can see what comes after this command:

I don't know what causes this problem or how i can turn this off.

The Mover process is scheduled at 3:00 AM so it is not caused by this i think.

I don't know for sure (don't use Plex), but it seems related to transcoding, and that's known for very heavy machine demands.

Look at Plex scheduled tasks under Server settings. By default this is set to run daily starting at 02:00am.