Hi,
I suggest to recreate the RAID 1 since breaking it didn't help. Once done, please post the output of the command # /var/lib/fai/config/QlustarInstaller/StorageManager.py
Here is the requested output:
# /var/lib/fai/config/QlustarInstaller/StorageManager.py Disk /dev/sda: 419.16 GiB, LOGICAL VOLUME
Disk /dev/sdb: 9.1 TiB, LOGICAL VOLUME
(note that I typed the output above in, so the formatting might differ).
Best, Dave