I've been shutting off my hard drives but found that anything short of unmounting them caused them to be awoken frequently by random processes with timer-based

I've been shutting off my hard drives but found that anything short of unmounting them caused them to be awoken frequently by random processes with timer-based disk access. My solution was to move all my online use-cases to a separate SSD and mount the HDDs only when I need them for a manual process. E.g. when I want to watch a movie I have downloaded, I'll mount the disk pool and copy it to the SSD (although my internet is fast enough that just downloading it again is usually faster than the manual process).