Bug was caught on preseeding Debian 7.6.0/i386, but I beleive it will
work for any other installation on dmraid enabled box. In my case
dmraid=true was added to kernel options of latest netboot kernel.
Installer insert dmraid module and create device, say /dev/mapper/asr_raid
When partitions are created this device split into /dev/mapper/asr_raidp1
asr_raidp2 and others.
I have two v60x servers with AIC-7902 HostRAID and they behave different.
In the real kernel booting devices will be named /dev/mapper/asr_raid1
asr_raid2 and others. (without p). So initramfs will fail to boot if
d-i will use device names as boot names. this is first bug and it is
most serious. As a workaround I used ln -s asr_raid2 asr_raidp2,
booted, refreshed fstab and update-grub.
On the other server d-i used UUIDs as boot names and it fail to load
because kernel find and link /dev/s* devices to UUID devices, then
load dmraid, which make sd devices busy and initramfs fail to load
root (by the way it will still has asr_raidp device in resume
environment variable). As a workaround I edited grub boot list,
booted, edited fstab and update-grub. This is bug number two.
Server intallations differs: first used dmraid=true in kernel boot
options, second had 'd-i disk-detect/dmraid/enable boolean true'
in preseed file. Don't know if it make sense.
Also initramfs complain about dm_raid45 module and I don't know
if its a bug number three or not.