I have 2x it hdd's in software raid with mdadm which I use as my backup storage. My server mounts the array, writes the backup, unmounts the array, spins down the disks and puts them to sleep completely automatically every night at 1am. They never wake or spin up at all during the day.
mdadm --stop /dev/mdX should at least tell you whether or not mdadm is causing the spinning.
You can try and figure out what's accessing the array:
fatrace | grep /mnt/mountpoint/
This will show you the process, type of access (read, write, open, etc), and path. If you don't see anything right away just leave it running for a bit.
Never had mdadm causing that. I have a raid5 array that's used only for backup once a day and it is mounted 24/7, and the disks are off for 23hba day more or less ...
Get an anti-hero to protect the data thieves?
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