Recovery Console:

Set Boot mode to recovery in “RecoveryManager” at https://config.stratoserver.net/ Wait for 15-20min!! until “ServerData” Serverstatus shows: Installtion finished

log in to recovery via

ssh root@IP   # recovery root passwd is shown in "Serverdata"

mount /dev/md127 /mnt/    # system partition
mount /dev/md126 /mnt/boot/    # boot partition

to re-install grub, you need to chroot

mount -o bind /dev /mnt/dev
mount -t proc none  /mnt/proc/
mount -t sysfs none /mnt/sys

chroot /mnt
update-grub

grub-install /dev/sda
grub-install /dev/sdb