Software RAID GRUB Fix
Fix Software RAID1 GRUB as root on booted system if GRUB is installed on /dev/sda:
grub-install --modules=mdraid1x /dev/sdb update-grub /dev/sdb
Also, confirm GRUB is installed both drives:
dpkg-reconfigure grub-pc
Fix Grub booting not reading config:
vi /etc/default/grub
Add rootdelay=10 GRUB_CMDLINE_LINUX_DEFAULT to:
GRUB_CMDLINE_LINUX_DEFAULT="quiet rootdelay=10"