Comment 6 for bug 1206238

It is hard to get the machine in question into this state again, to get the explicit output from the grub ls command. It would list all my partitions other than the one which was switched to raid1, which was absent en-toto.

As for configuration. This is a pure LVM setup, using the MD raid personality for raid:1 underneath. There is no mdadm configuration as they are built by LVM. Looking at that device in dmsetup table it looks something like this:

    datavg-home: 0 524288000 raid raid1 3 0 region_size 1024 2 252:6 252:7 252:8 252:9

So it drops into the following piece of grub_lvm_detect():

                  else if (grub_memcmp (p, "raid", sizeof ("raid") - 1)
                           == 0 && (p[sizeof ("raid") - 1] >= '4'
                                    && p[sizeof ("raid") - 1] <= '6')
                           && p[sizeof ("raidX") - 1] == '"')
                    {

Not that this specifically only handles three types of raid:N 4, 5, and 6. With this form of symetric mirroring we have raid:1.