I installed Ubuntu 18.04 as a second OS on a computer which had Windows 7 already installed. The computer had an Intel RST FakeRAID level 5. After a good deal of messing around, I finally followed the instructions in the top answer to this question. This worked fine… until one of my hard drives failed.
I replaced the drive, and booted into Windows, where I rebuilt the RAID volume with Intel Rapid Storage Technology.
Now Windows boots and functions perfectly fine, but Ubuntu hangs while booting.
What’s going on, and how can I fix this? According to this page, mdadm is supposed to be able to handle Intel RST.
I tried to boot into recovery mode, and it dropped me to the initramfs shell, after telling me that fsck had found errors on my last partition.
Because I suspected that the RAID format used by the Intel RST tool in Windows was different from the RAID format used by mdadm in Linux, I was afraid to repair the filesystem with fsck. But after I had verified that the raid had been detected correctly, I finally ran fsck on the last partition. This solved the problem.