I started a new build on UnRAID 6.8.3 stable, I waited patiently for 6.9 before trying to add a cache drive because I read in the blog about the new SSD changes.
Anyway now on 6.9 I go to add a single cache drive (1TB Samsung SSD) as BTRFS encrypted (auto and just BTRFS don't work either).
I start the array, format the SSD cache drive, error message:
Unmountable: Missing encryption key (next to the cache drive),
The rest of the array which is also encrypted mounts fine.
If I set the cache drive to just BTRFS with no encrption, after start the array next to the cache drive it says:
2) Unmountable: not mounted
I have tried multiple SSD drives to make sure its not the drive.