I got disks to show when add dmraid=true when booting install-media. After successful install system failed to boot up and fall to busybox.

I had similar problems when I installed Arch. I fixed it by adding dm_mod, dm_mirror and dmraid to mkinitcpio.conf.

I've used rescue-cd and found out that dmraid package is installed. Maybe kernel has no dmraid support and it cannot read disks.

FakeRAID is software RAID with a boot ROM. The kernel doesn't see the RAID, but rather sees the individual drives. The dmraid executable reads the (proprietary) metadata from the drives, and then tells device-mapper (dm_mod et al) to assemble the RAID set.

You've basically identified the problem yourself already: The initrd probably lacks dmraid support. Obviously the kernel can see the drives and dmraid is present and able to activate the array, since you were able to install the OS. That leaves the initrd.

Unless the initrd loads the relevant device-mapper modules and runs dmraid to assemble the RAID, the RAID device just won't be there. You need to add dmraid to your initrd somehow.

Unfortunately, I don't know the specifics when it comes to Debian, but now that you know what you're looking for, perhaps the Debian documentation will be of some help.

Hello and welcome to LQ.

It is a risky install and not really worth trying. Fake raids have been known to show to distros as various things. Different versions of distro may show different media.

Once in a while you can get the card to present dedicated sata or what ever to the OS on upper channels on some models.

I really don't understand your reasons for making this claim.

Not all distributions have installers that support FakeRAID, so it's true that getting it to work can be somewhat difficult and involve hand-crafting an initrd, but the term "risky" seems to suggest that the end result might not be stable or work properly.

FakeRAID is simply a form of software RAID. The only difference between that and an md setup is the vendor-specific metadata format. A FakeRAID array is assembled and maintained by device-mapper, and surely you're not arguing that the dm subsystem, which forms the basis for LVM, is somehow unreliable?
Some years back (2000-ish) you might be able to find a dedicated Linux driver for a FakeRAID controller. I know Promise made one for their FastTrack series of ATA/IDE FakeRAID systems, and I even used it on one occasion. However, these drivers were neither open nor free.

These days, FakeRAID on Linux always relies on the OS seeing the actual SATA controllers and channels, and the RAID is built by directly accessing the metadata on each drive. Exactly like md, in fact.