[Bug 1206238] Re: grub2 LVM support does not handle MD raid1 style mirrored volumes, completely ignoring such volumes

[Andy Whitcroft]

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.

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https://bugs.launchpad.net/bugs/1206238

Title:
  grub2 LVM support does not handle MD raid1 style mirrored volumes,
  completely ignoring such volumes

Status in “grub2” package in Ubuntu:
  Triaged

Bug description:
  grub2 LVM support handles MD raid 4.5 and 6 but not raid1.  If you
  make your boot or root raid1 it is no longer able to even list the
  volumes.  It is therefore possible to boot your system, add a mirror,
  reboot and have no system at all.  I would guess raid1 would be a
  degenerate case of the mirror support that already exists.

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: grub2 (not installed)
  ProcVersionSignature: Ubuntu 3.10.0-1.2~unstable201306041951-generic 3.10.0-rc4
  Uname: Linux 3.10.0-1-generic x86_64
  ApportVersion: 2.9.2-0ubuntu8.1
  Architecture: amd64
  Date: Mon Jul 29 20:27:49 2013
  EcryptfsInUse: Yes
  MarkForUpload: True
  SourcePackage: grub2
  UpgradeStatus: Upgraded to raring on 2013-02-26 (153 days ago)

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