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........
mdadm --manage /dev/md1 --add /dev/sdb1
mdadm: metadata format 00.90 unknown, ignored.
mdadm: metadata format 00.90 unknown, ignored.
mdadm: metadata format 00.90 unknown, ignored.
mdadm: /dev/sdb1 not large enough to join array
md1's first primary member /dev/sda3 has 57394 cylinders while the /dev/sdb1 has 57393 (1 less cylinder) which is why it won't work.
fdisk -l /dev/sda3
Disk /dev/sda3: 47........
Nice General Linux RAID 1 GuideFull examples/tutorials that should work for any Linux system using GRUB or LILO as the boot loader.
This is the only tutorial I've seen that clearly shows how you can convert an existing non-RAID system to software RAID1 remotely, without ever having to be at the computer. This is important for people who co-locate or rent dedicated servers that they may not have physical access to in a timely manner.
https://alioth.debia........