Linux software raid or md raid can be used as a boot device. But only if that raid device is a RAID-1 or mirror.
As boot loader, grub in this case, does not know anything about software raid that is managed by kernel, it needs to be installed on both devices on that software mirror.
Select disk and partition where Your /boot resides.
Countdown starts from zero, so /dev/sda3, if it is Your first drive, becomes hd(0,2)
Filesystem type is ext2fs, partition type 0xfd
install grub into boot sector of that hard drive
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 16 sectors are embedded.
Running "install /boot/grub/stage1 (hd0) (hd0)1+16 p (hd0,0)/boot/grub/stage2 /boot/
repeat that on the other hard drive, which is probably (hd1)
and exit grub
if You do not know which device is which, look at
and edit it if needed.
The editing bit goes specially for cciss driver.