HOWTO: initramfs with optional RAID|LUKS|LVM|TOI|AUFS

[d-fens]

hi,

i'm trying to get a new nas serverup with following layout

/dev/sda1 boot ext2
/dev/sda2 luks crypted partition

mirrored on sdb

so i need the initramfs to first decrypt /dev/sda2 and /dev/sdb2 and then create the zfs pool containing everything needed from /dev/mapper/crypt-a + /dev/mapper/crypt-b
i tried with genkernel but it just seems to allow luksopen one device, and not two (or more)
is this the tool i need to get it running and do you have any hints?