I want to configure an automatic installation of ubuntu server 14.
I need two partitions on one single raid array. One for the os and one for data.
As i can see it is only possible to partitioning the hard dirves and set up multiple raids.
But it is very important for me to have only one array running with two partitions on it.

Is there any way to preseed this setup? If not, is there any way to manually partition the raid array in bash during the installation?

PS: i can not use lvm in my setup

Size of drives?
How do you want to partition?
What type of RAID array to oyu want to use?

I want to use 2x 2TB in an raid1 array.

layout:
32GB / ext4
remaining_space /media/data ext4

AFAIK that's only possible with a hardware raid controller.

Out of interest, why can't you use lvm? I can't think of any reason.

You can also use software raid.
I dont know, which options you can select during installation, but try it out.
You can also buy a book for ubuntu administration.

My supervisor asked me to do it without because our custom nas administration software does not support lvm administration.
Since it is not possible without, i try to do it with lvm...

Any hints how to preseed this setup with lvm?

At this moment i preseed the raid this way:

debconf-set partman-auto/method "raid"
debconf-set partman-auto/disk "/dev/sda /dev/sdb"
debconf-set partman-auto-raid/recipe "1 2 0 ext4 / /dev/sda#/dev/sdb."
debconf-set partman-auto/expert_recipe "boot-root :: \
1024 10 1000000000000000 raid \
\$primary{ } \
method{ raid } \
format{ } \
."
debconf-set grub-installer/bootdev "/dev/sda /dev/sdb"

I am setting the presseds in a bash script, because there are a few other hardware setups which have to be supported by the installer.

@Keruskerfuerst
I tried to configure this setup with the standard ubuntu server installer and i am not able to create multiple partitions on a software raid1.
The only thing i can do is to setup two partitions on the disks and create two raid arrays...

Ok, it seems to be possible, but I had to create the raid and the partitions in it with a systemrescue CD in my test VM. I think you're also better off if you keep the boot partition outside the raid. I had problems booting when I removed one of the disk, but not the other. When I had the problem with booting, I needed to re-add the previously removed disk to the raid and let it finish the sync. Only then the raid would boot again.

I decided to use lvm now.

i am using this preseeds:

debconf-set partman-auto-raid/recipe "
1 2 0 ext3 /boot \
/dev/sda1#/dev/sdb1 \
. \
1 2 0 lvm - \
/dev/sda5#/dev/sdb5 \
.
"

debconf-set partman-auto/expert_recipe " multiraid :: \
100 512 256 raid \
\$lvmignore{ } \
\$primary{ } \
method{ raid } \
. \
900 5000 4000 raid \
\$lvmignore{ } \
method{ raid } \
. \
700 5000 4000 ext4 \
\$defaultignore{ } \
\$lvmok{ } \
method{ format } \
format{ } \
use_filesystem{ } \
filesystem{ ext4 } \
mountpoint{ / } \
. \
64 512 300% linux-swap \
\$defaultignore{ } \
\$lvmok{ } \
method{ swap } \
format{ } \
. \
100 1000 1000000000 ext4 \
\$defaultignore{ } \
\$lvmok{ } \
method{ format } \
format{ } \
use_filesystem{ } \
filesystem{ ext4 } \
mountpoint{ /data } \
."


The problem right now is the second raid array.
Any hint how to preseed the boot partition not in an extra array?
I tried to configure the boot partition not as an raid but as ext3 and removed the array from partman-auto-raid/recipe which causes the installer to stuck after partitioning without any error...