+1
In a three hard drive (each is partitioned differently) Ubuntu/Ubuntu
Studio 9.10 rig I too do an independent install of one OS per drive (by
powering the PC down, disconnecting the data cables of all the HD's
except the one I'm installing to, then repeating the process for the
remaining drives) in order to avoid wasting more time dealing with
broken GRUB2's.
For anyone else who may wish to explore this approach, there's a
caveat:
Twice since installing '9.10, Ubuntu's updates have included a few for
GRUB2. The first time this occurred I let the updates proceed and the
updated GRUB2 tied all the hard drives together thus defeating the
purpose of doing an independent OS install per hard drive.
Since I was setting up a new (to me) machine anyway, I reformatted the
drives and reinstalled the operating systems while making a mental note
to scrutinize each new list of updates for any future signs of an
impending GRUB2 update.
Upon eventually finding said signs, I powered down, disconnected all of
the drives except the one whose OS I wished to update, and then repeated
the routine for each of the other drives.
I realize this is not the correct way of dealing with a broken GRUB2
but I'm spoiled from my Mac days.