Usually when I come across a system like this, Ijust flash the firmware to an IT mode so we get just an AHCI system with JBOD, but sometimes it is not practical for remote systems or if we fear that flashing is too risky if something goes wrong.
In this case, we unfortunately have to use LSI/Broadcom proprietary CLI tools (megacli) to even make the drives visible.
Step 1 - Download MegaCLI
The official broadcom packages lack .deb packages and only have .rpm for........
Done on Centos 7.3 very important as clearly based on older guides it was a lot easier and more simpler! Hint do not use grub2-install!
If you have trouble booting after this check this CentOS mdadm RAID booting/fixing guide.
One huge caveat if you are an oldschool user or sysadmin who has avoided UEFIbooting
The nor........