Hard disks auto-spinning-down

[Mark Fletcher <mark27q1@gmail.com>]

Since a fresh install of buster, an external USB3 hard disk cage from 
Terramaster that I own is not automatically spinning down the disks in 
it when they go unused for a time.

I used a previous generation of the cage with Stretch previously, it 
spun down the disks when they were not in use (actually a little too 
quickly for my taste) reliably and I don't recall doing anything to make 
that happen.

Any thoughts on where I might look to find settings that can be tweaked 
to make it spin down when idle? A friend of mine uses the same cage with 
a Mac and says it spins down when not in use, so I feel like I should be 
able to do it somehow.

The only thing I can think of that I've tweaked since installing buster 
is to disable suspend, as I didn't want the whole computer suspending 
when I was away for a bit, as this computer does a lot of background 
processing. I wonder if I overdid that and disabled something I should 
have left enabled? The solution to that problem involved disabling a 
couple of systemd targets.

I just re-googled that problem because I couldn't remember what targets 
I disabled -- and now I see on the wiki that they are sleep.target 
hibernate.target suspend.target and hybrid-sleep.target. The wiki says 
to do "systemctl mask" on those targets but I suspect I followed someone 
else's advice and did "systemctl disable" on those targets.

Any link to this problem? Otherwise where should I look?

Thanks

Mark