Also does grub do the right thing when you are using software raid?
I dont know if it has been fixed or not
In the past grub didn't install on both drives boot sectors. In addition grub installs fail on really large (1.6T) 3ware raid arrays under RHL-9. I can't really test it as I can't reinstall my main file server.
I've seen that reported before but never had a chance to find out. There are several reports which don't mention 3ware and grub has had some signed v unsigned problems fixed so it may be this problem is fixed now.
(It has some 64bit issues too which will begin to bite at 2Tb (4T-sectors)