grub>First, you'll have to type this, and you will get the location of grub setup files:
(hd1,0)So, if you have SATA, (hd0,0) stands for /dev/sda, and (hd1,0) stands for /dev/sdb - it will be hd* for IDE. So, to make sure you have grub install on both MBR on both drives of the mirror, type this:
grub>device (hd0) /dev/sdbgrub>root (hd0,0) and then:grub>setup (hd0)grub>quitThis actually changes MBR to /dev/sdb (not the usual /dev/sda) and copies necessary files to boot. After reboot, it will still load grub from /dev/sda, but if something happens to it, it will successfully start your Linux from /dev/sdb.