Maybe I'll have to take another look at it when I have some free time, although I vaguely remember something not working right with the standard mdraid tools. According to this post, it seems to be a slightly customized version: https://serverfault.com/questions/568166/how-to-recover-an-m...

Thinking back on this situation made me remember the terrible thermals in that old NAS. I had to replace the (fanless) PSU 2 times because it was always blowing up and creating sparks/smoke. Lol good times.

On their older models, the webUI did something funky with LUKS encryption passwords meaning you couldn't actually just mount the disks in another Linux computer as you coukd never unlock them. I have memories of us having to do the encryption setup and unlock via ssh so we could mount the drives in something else in the event of a failure (though we retired that box over 5 years ago so my memory might be rusty).

edit: my memory _is_ rusty; it was a QNAP box we had to do that with not Synology.