You didn't write anything like, which distro you use (Am I blind?). Today I almost destroyed my server, because I was really pi**ed off of not working grub-install. I used to have GRUB error 17, when trying to do that.
So I have better solution, how to install very easily and very quickly grub to multiple drives in raid.
If you can boot your system (after install or from live distro), and have Debian Wheezy (in my case ver 7.2), you can just type following command:
(you must be root when doing this!!!)
I was pressing just enter, enter, enter and last screen, there was a question, into which devices I want to install the GRUB! :-) Just by your space choose all physical drives (do not choose /dev/md devices, just /dev/sdb /dev/sdc and so on and neither don't choose /dev/sdb1 or /dev/sdb2, just only devices without numbers!) In my example /dev/sdb /dev/sdc dev/sdd /dev/sde not /dev/sdb1... Then you go next and wait few seconds (about 30 or 45 seconds to finish) and get a next bier for a celebretion, because YOU DID IT!
Ubuntu-server 12.04 LTS ask you at the ending of installation, if you want to install grub into all devices. Debian does not have it.
After this solution, it does not matter on which hard drive boots earlier or later, it will boot everytime.