If you’ve had a previously configured Raid Set on an Areca RAID controller and it all of a sudden disappears it can sometimes be salvaged.

In the RAID BIOS:

Raid Set Function -> Rescue Raid

You’re then prompted to “Enter the Operation Key.” This is ambiguous in the documentation and there’s also a mispelling for one of the commands but here’s the process you should try (this is specific to the Areca 1883 controller and may be slightly different on other controllers):

Boot #1

Raid Set Function -> Rescue Raid

Enter Operation Key:

RESCUE

then reboot.

Boot #2

Raid Set Function -> Rescue Raid

Enter Operation Key:

SIGNAT

(this is misspelled in the documentation as “SIGANT”)

then before rebooting…

Raid Set Function -> Rescue Raid

Enter Operation Key:

LeVeL2ReScUe

(this command is not in the documentation)

then reboot.

Boot #3:

Raid Set Function -> Rescue Raid

Enter Operation Key:

SIGNAT

then reboot a final time.

You will likely need to boot into a rescue disk to reinstall your boot loader before the OS will boot on its own. You also may need to change the partition number in the GRUB config.