Note that with the UUID-based raid assembly https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/158918/comments/33 the mdadm.conf file is not used to store ARRAY definitions any more.
Thus the (UUID) list of raid devices required to mount the rootfs must be stored in a separate file within initramfs.
Note that with the UUID-based raid assembly /bugs.launchpad .net/ubuntu/ +source/ mdadm/+ bug/158918/ comments/ 33
https:/
the mdadm.conf file is not used to store ARRAY definitions any more.
Thus the (UUID) list of raid devices required to mount the rootfs must be stored in a separate file within initramfs.