grub rescue read or write sector outside of partition

["Dale Carstensen" <dlc@lampinc.com>]

I had a drive fail, and it is the one that had grub on it.
It had parts of two RAID-6 partitions, too.  So I bought a
new drive and added partitions on it to replace the failed
RAID-6 parts.  That was still booting OK from the failed
drive, but then I updated the kernel, and I decided to also
install a new grub on the new drive.

That seemed to go OK until I tried to reboot.  I landed in
grub rescue.  Fortunately I have several computers, so I can
look up documentation, etc. without my main desktop functioning.
Somewhere I found that grub rescue has only a few commands, none
of them "help" or a list of commands, and no TAB-expansions.
Well, they seem to be ls, set, unset and insmod.  Supposedly,
running insmod normal, then normal, will get back to the
fuller set of commands with help, but that's where it gets
the "outside of partition" error, it seems.

I can ls the /boot/grub/i386-pc/ directory, where normal.mod
is, so I would think grub rescue could find and read normal.mod,
too, but, I guess not.

So, set debug=all helped a little, expanding the message
from just something like (I'd have to keep trying to
reboot to get it verbatim) read or write bad, to
the specific size of the partition (in decimal, around
175 million 512-byte blocks) and the sector it is trying
to read (read.c:461) (in hexadecimal), around 10 million.
But 10 million hex really is larger than 175 million
decimal.

So maybe my BIOS has some limitation on how deep it can
read into this 2 TB drive, or maybe the drive having
hardware sectors of 4096 bytes replacing one with
512 confuses grub.  But the old drive with the failures
gets the same problem.

It's gentoo, grub2 (I could look up the version once it's
running again), 64-bit (although grub seems not to really
notice 32- vs 64-bit, or the kernel, so I'm not sure it's
just smart or really dumb), and, like I say, the / partition
is RAID-6, including /boot.  I'm going to try making a
non-RAID /boot, maybe later I'll try making it RAID-1,
to see if that helps.

Any advise?

Thanks.

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