Minor We don't yet support all-MDT systems, but I'm sure it is only a matter of time until we do. I think the main limitation is that we don't allow clients to use the filesystem until the MDS has connected to at least one OST, to prevent clients just getting errors when trying to use the filesystem (before DoM).
We probably also need some testing to ensure we allow DoM file creates without OST components even if no OSTs are connected. We might also need to lift the 1GB dom_stripesize limit in that case.
Finally, we might need to handle MDT and OST on the same node better during recovery, but it might also just work since the MDT always uses the same connection UUID.
