ok i just found the solution,

on the grub.cfg

the set root line must be set root=md/0 on not set root=md0...

Hello,

i try to install arch linux on zfs + /boot on mdadm but i have an issue.

At boot i have this error:
Error: device 'ZFS=zroot/' not found

here is how i install my system:

nano /etc/pacman.conf ->
[demz-repo-archiso]
Server = http://demizerone.com/$repo/$arch

pacman-key -r 0EE7A126 ...