Description of Problem:
The new disk druid partitioner will display pre-existing RAID auto-detect
partitions as ext2 filesystems or as standard Linux partitions (I don't
recall the exact spelling, sorry). This is confusing. If they're raid
partitions, they should be identified as such, even if there's nothing the
installer is going to do about them.
Hmm... software raid partitions show up as such for me. Are the partitions of
type 0xfd if you look at them in fdisk (Linux raid autodetect)?
D'oh, never mind. For some reason, the partitions were not of type 0xfd, even
though I was sure they were. Perhaps parted messed them up, or perhaps I
created the partitions with parted, and failed to change their types with fdisk
later on. Well, anyway, it was my fault. Sorry about the noise.