Hi @AlexQ , thanks for reporting the issue
raid's should be supported in updated versions of elive, but I see that you are using a beta version, so there should be a problem somewhere
Can you tell me more details on how you configured this raid system? did you created it on linux or it is configured from the bios? 
i need to know that in order to try reproducing the same scenario in a virtual box
A helpfull command that you can run to see if is detected somewhat is:
sudo partitions-list --show-all --show-raw --show-disks
it should show the raid structure just like other elements, like maybe the disks individually
