Grub problem while rebuilding my server as a virtual host

Installing Centos6.3 and setting up software raid

Disk setup:
500Mb software raid partition for /boot (on sda and sdb)
Create LVM raid partitions for the rest (and left over make ext4 partition)
In the LV - about the same swap as memory and the rest as /

Had a problem with grub (error 15), this fixed it:

grub> device (hd0) /dev/sda
grub> device (hd1) /dev/sdb
grub> root (hd0,0)
grub> setup (hd0)
grub> root (hd1,0)
grub> setup (hd1)
grub> quit