when a raid device is build from a group of raid partitions the selected personalities should be loaded on init using an initrd image, otherwise, when the system boots and the kernel autodetects the raid partitions an error would show and the autodetected raid device would be aborted. for sure, it could be started later from the initscripts, but making it start on kernel load would make it easier to have a RAID root partition and has no drawback. all is needed is to set a variable telling which personalities were selected on install and running $(mkinitrd --with=raid?) as required.
This should happen automatically -- we've tested RAID1 on root recently and had it work through exactly the mechansim you describe. What problem are you actually seeing?
works better than i expected, you can get software raid even on scsi people, you are amazing :)
even on SCSI + RAID + root :)