Installer fails for software RAID

[Jared Rhine]

I've been unable to produce a working software RAID (md, not fakeraid) 
configuration using the alternate CD installers for Feisty Herds 3, 4, 
and 5.

I was hoping to get a confirm/deny or workaround from this users list 
before filing a bug.  I hate reading or working on problem reports 
involving RAID, LVM, GRUB, and the like because so many of these boil 
down to user error.  But this one seems to be generated by the Ubuntu 
installer using a pretty standard configuration.

The target configuration isn't particularly strange; I had this same (or 
similar) configuration running on this box before.  It puts root (/) on 
RAID 0, though a separate non-RAID /boot is used (so no clever tricks 
should be needed).

SATA drives, with both sda and sdb partitioned identically.

sd[ab]1: /boot, ext3, bootable, 1Gb
sd[ab]2: /srv/backup, ext3, 20Gb
sd[ab]3: swap, 5Gb
sd[ab]4: physical RAID, 134Gb
md0: RAID-0 from sd[ab]4, root (/), ext3

Install goes fine.  On reboot, I get output from the initramfs 
(shortened slightly):

* Mounting root file system
* Loading MD modules
* md: raid0 personality registered/Success: loaded module raid0.
* Begin: Assembling all MD arrays
* mdadm: No devices listed in conf file were found.
* Failure: failed to assemble all arrays
* Waiting for root file system...
[...]
* Mounting /root/dev on /dev/.static/dev failed: No such file...
* Target filesystem doesn't have /sbin/init

When sitting at the initramfs prompt, I can immediately "mdadm 
--assemble /dev/md0" and the drives gets properly assembled to the point 
I can mount it and poke around and see what appears to be a fully 
functioning root partition.  It seems to even have the right RAID UUID, 
though problems with UUIDs would be consistent with the mdadm "no 
devices listed in conf file" error while still being able to --assemble 
from the initramfs just fine.

I get the same problem with both this physical machine and a virtual 
machine (Parallels) install.

Can anyone create a bootable RAID configuration using the above scheme 
in Feisty?

Suggestions, even RTFMs, are welcome.

-- Jared