@joka-fx Welcome to the Rockstor community. I’m afraid I’m going to have to be a little shorter in my answer than I would like as I have to dash but just wanted to chip in that I have seen this failure of the install program to initialize the IRST properly. For me I think I noticed that my bios boot stated that the drive was still initializing and I saw the absence of md126 device with it’s 3 partitions ie rockstor_rockstor on /dev/md126p3. I believe there to be a bug in the installer and unfortunately I haven’t made good enough notes on it just yet. But from a quick look at what notes I did make it seems that when I installed again I took a slightly different path through the installer ie non auto and btrfs scheme and then the install ended up as expected.
My notes state I also went back and ticked auto but once I’d first done non auto and btrfs scheme things proceeded as expected. Obviously as you did I selected the presented bios disk.
Sorry not very clear but I have seen this and it looks like during install one has to do non auto and select btrfs scheme, first then the bios raid is initialized correctly. Once done the disks page should look like the image in the following post:
There was a forum post that in turn links to an older one re “Reinstall activation” that may help with that question.
Thanks for the interest and let us know how that install quirk goes, we have inherited it I’m afraid as we use the installer neat from our CentOS base and it’s a subtle problem that is time consuming to root out. I will try a re-install on my bios raid system here and report back but sorry got to dash now.