Comment 1 for bug 13430

I had a similar problem when installing on my system. I have an ide disk that I
use for extra storage, but I run my system on a scsi raid array (I boot from scsi).
  1) When running the installer in normal mode, it automatically installed grub
on the ide disk. The installer should have detected multiple disks and asked
which to install grub on. I think it just ignored my scsi disks.
  2) There is an inherent problem with installing on this setup because grub
uses the bios to detect disks, so I'm not sure how easily this can be fixed.
When I install, I boot from my ide cdrom drive. This causes the bios to order
the disks like this: ide (hd0), scsi (hd1-hd5). So if I tell grub to install to
the first scsi disk, it uses (hd1,0) as the root device in its config. But then,
after the installer completes, I reboot off of scsi, the bios reorders the
disks: scsi (hd0), ide (hd1), scsi (hd2-hd5). So now grub doesn't know where to
find the kernel because it is looking in (hd1,0), which is the wrong disk.

I solved this by unplugging the ide disk during installation. A better solution
is desirable, but it will probably require some voodoo because I can't think of
any way for grub-install to know my system is setup this way without asking.