grub won't install on a disk

[R. W. Rodolico]

Attempting to install grub2 on the second member of a boot RAID-1
partition. The boot partition is /dev/md0, consisting of /dev/sda1 and
/dev/sdb1. Contents of /proc/mdstat
====================================================
Personalities : [raid1] [raid6] [raid5] [raid4]
md1 : active (auto-read-only) raid5 sde[0] sdd[3] sdc[1]
      3907025920 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3]
[UUU]

md0 : active raid1 sda1[3] sdb1[2]
      14931290 blocks super 1.2 [2/2] [UU]

unused devices: <none>
====================================================
(note, md1 can be safely ignored, has nothing to do with boot process)

Executing the command grub-install /dev/sdb returns
====================================================
/usr/sbin/grub-probe: error: no such disk.
Auto-detection of a filesystem of /dev/md0 failed.
Please report this together with the output of "/usr/sbin/grub-probe
--device-map=/boot/grub/device.map --target=fs -v /boot/grub" to
<address@hidden>
====================================================

Output of '/usr/sbin/grub-probe --device-map=/boot/grub/device.map
--target=fs -v /boot/grub' is
====================================================
/usr/sbin/grub-probe: info: Cannot stat
`/dev/disk/by-id/ata-STT_FTM16GL25V_I645132-MJBY-819A007', skipping.
/usr/sbin/grub-probe: info: Cannot stat
`/dev/disk/by-id/usb-USB_2.0_USB_Flash_Drive_5a146bf7420274-0:0', skipping.
/usr/sbin/grub-probe: info: the size of hd1 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd1 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd2 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd2 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd3 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd3 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd1 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd1 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd2 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd2 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd3 is 3907029168.
/usr/sbin/grub-probe: info: the size of hd3 is 3907029168.
/usr/sbin/grub-probe: info: changing current directory to /dev.
/usr/sbin/grub-probe: info: changing current directory to virtuals.
/usr/sbin/grub-probe: info: changing current directory to dri.
/usr/sbin/grub-probe: info: changing current directory to snd.
/usr/sbin/grub-probe: info: changing current directory to by-path.
/usr/sbin/grub-probe: info: changing current directory to net.
/usr/sbin/grub-probe: info: changing current directory to shm.
/usr/sbin/grub-probe: info: changing current directory to mapper.
/usr/sbin/grub-probe: info: opening md/0.
/usr/sbin/grub-probe: error: no such disk.
====================================================

This is a production system I took down over the holiday's here in the
US to try and repair. It is working just fine (off, I assume, the grub
on /dev/sda), so this is not critical. However, I would like to fix it
in case /dev/sda fails and must be removed.

I updated the system today, 28 May 2012, so it should have the latest
patches, etc.. in it.

NOTE: this is a Xen DOM0 Hypervisor, running the Debian Squeeze Xen
kernel. Output of uname -a
====================================================
Linux REMOVED_SYSTEM_NAME 2.6.32-5-xen-amd64 #1 SMP Sun May 6 08:57:29
UTC 2012 x86_64 GNU/Linux
=====================================================

Thank you,

Rod