Turns out this is a known issue with initramfs-tools. It's simply not waiting for the root devices properly.
Adding rootdelay=30 to kernel parameters was good enough for me. While this isn't a debian-installer bug, it would be nice if debian-installer provided workaround to all RAID/LVM users by default until it's fixed in initramfs-tools. -- To UNSUBSCRIBE, email to debian-boot-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
