Comment 28 for bug 1828617

Some further references:

Each part of the OSD is queried for its underlying block device using blkid:

  https://github.com/ceph/ceph/blob/luminous/src/ceph-volume/ceph_volume/devices/lvm/activate.py#L114

I guess that if the block device was not visible/present at the point that code runs during activate, then the symlink for the block.db or block.wal devices would not be created, causing the OSD to fail to start.