d-i partman-auto/method string raid
d-i partman-auto/disk string /dev/sda /dev/sdb /dev/sdc /dev/sdd

d-i partman-auto/expert_recipe string
    multiraid::
        512 10 512 raid
            $primary{ }
            method{ raid }
        .
        2000 20 3000 raid
            method{ raid }
        .
        10000 30 4000000 raid
            method { raid }
        .
        1000 40 1000 linux-swap
            method { swap }
            format { }
        .

d-i partman-auto-raid/recipe string
        10 4 0 ext4 /boot
            /dev/sda1#/dev/sdb1#/dev/sdc1#/dev/sdd1
        .
        10 4 0 ext4 /
            /dev/sda5#/dev/sdb5#/dev/sdc5#/dev/sdd5
        .
        10 4 0 ext4 /var/lib/vz
            /dev/sda7#/dev/sdb7#/dev/sdc7#/dev/sdd7
        .

d-i partman-md/confirm boolean true
d-i partman-md/device_remove_md boolean true

d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true

d-i mdadm/boot_degraded boolean true

# This command is run immediately before the partitioner starts. It may be
# useful to apply dynamic partitioner preseeding that depends on the state
# of the disks (which may not be visible when preseed/early_command runs).
d-i partman/early_command string mdadm --stop /dev/md127 && mdadm --remove /dev/md127