kickstart partitioning fails

[Franck Pommereau]

Dear all,

I'm trying to install Ubuntu-server on a cluster, so I've set-up a
server to enable PXE boot and network installation. Cluster's nodes
have two identical 8GB drives and I want to use RAID0 on /, I've read
that it is then mandatory to have a /boot with RAID1. So, I use a
kickstart script with the following:

clearpart --drives=sda,sdb --all --initlabel
part raid.01 --size 512  --ondisk sda
part raid.02 --size 512  --ondisk sdb
part raid.11 --size 7680 --ondisk sda
part raid.12 --size 7680 --ondisk sdb
raid /boot --level=1 --device=md0 raid.01 raid.02
raid / --level=0 --device=md1 raid.11 raid.12

When installation process comes to partitioning, a menu pops-up (first
problem) proposing to commit changes to sda only (second problem), and
then, partitioning fails (third problem). Looking at /var/log/partman,
I see that sdb is announced to be left unchanged, which contradicts my
kickstart script.

Moreover, an option --fstype=ext3 on raid lines is not recognised, so
I cannot tell the installation which filesystem it has to install.
(However, probably this is guessed from mountpoints.)

Exactly the same problem arises for various versions of ubuntu-server
(10.04.3-amd64, 11.04-i386 and 11.10-i386). I also tried on a virtual
machine and this is just the same.

Is there anything I'm missing? I'm really confused...
Many thanks in advance for any tip!

Cheers,
Franck