I’ve had the same issue and I’ve managed to link it to the Intro Detecting feature. Even though scheduled tasks may run between specific hours, for me most days the Intro Detecting task might keep running well beyond those hours, sometimes even 12 hours later. I’ve confirmed it’s definitely Intro Detecting that’s the culprit as I can see it working in the Plex Dashboard in the web app; it says what show it’s working on, and it’s always the same files that are open and causing a high load on the file server.
I can’t use Plex while detecting intros is stuck, but the high load on the file server drops instantly as soon as I stop or restart the Plex service.
It would work better if detecting intros gave up and failed on some files rather than getting stuck for too long on one file. It would also be better if there were an option to only ‘generate intro video markers’ when media is added instead of as a scheduled task of old media, that way you can have intro detection for new files at least.
Try turning off intro video markers as a scheduled task and see if you still get the high disk activity.
