Przed instalacją

cfdisk /dev/sda
sfdisk -d /dev/sda | sfdisk /dev/sdb
mdadm --create --level=1 --raid-devices=2 /dev/md1 /dev/sda1 /dev/sdb1
mdadm --create --level=1 --raid-devices=2 /dev/md2 /dev/sda2 /dev/sdb2

Po instalacji

mount /dev/md1 /mnt/target
xchroot /mnt/target
mdadm --detail --scan >>/etc/mdadm.conf
cat /etc/mdadm.conf
HOMEHOST <system>
MAILADDR root
ARRAY /dev/md1 metadata=1.2 name=vl:1 UUID=eeb80e78:eed65d73:20803cee:3b000001
ARRAY /dev/md2 metadata=1.2 name=vl:2 UUID=ffb74813:8c83ab2b:ce72db29:6b000002
cat /etc/dracut.conf
# PUT YOUR CONFIG IN separate files
# in /etc/dracut.conf.d named "<name>.conf"
# SEE man dracut.conf(5) for options
add_dracutmodules+=" mdraid "
hostonly="yes"
#cat /etc/modprobe.d/mdadm.conf
#options md_mod start_ro=1
xbps-reconfigure -fa
grub-install /dev/sdb
update-grub

More information

Refs