Cache_dirs scan level depth "auto" not enough?

I've had an ongoing issue with drives and their contents staying in cache_dirs memory for what seems like forever, but it's definitely much longer than needs to be. I've never gotten a straight forward answer as to why or what could be causing this issue, but I'm going to lay it all out in hopes that someone can shine some light: I currently have a 3 drive array, all contain parts of Movies and Television. When adding a new series in sonarr, any time I add a new series, drive 3 will spin

I have a suggestion, but I really don't know if it will help. Use the Tips and Tweaks plugin to decrease the vm.dirty* settings, from the defaults of 10 and 20, to 5 and 10, or even 2 and 3 (turn on the Help). This decreases the disk buffering the kernel uses, might decrease the memory pressure, and enable more of the directory entries to stay cached. What could cause a disk to spin up: - any write to the disk - any read of any part of the disk that has not been cached - any read