Why are my disks (almost) always active

[pkcyll]

I am using my Drivestor 2 Pro (AS3302T) under RAID 0
- a file server where I store my Pictures, Movies and Music folders (I am under MacOS)
- a TimeMachine backup

Ever since I put it in service, the disks have constantly been chatting, even when I am not accessing any local files or when the TimeMachine software is not running.

Being UN*X knowledgeable, even when running a terminal window on the local Linux server, the local kernel is barely doing anything (according to the usual commands)

So ... what's up????

Being a former Information Security person, I am starting to question whether I can trust what the Linux commands are showing me and whether the OS is actually doing plenty of work under the radar (such as bitcoin work, etc.)

Anyone else here has a similar situation?