If you boot from the 'old' device, you want the partitions on that device to be assembled in md0, md1,... as degraded arrays. When you boot from the 'new' device you want partitions from that device to become the mdX arrays.
Yep. We dealt with the issue by avoiding raidautorun and using mdassemble to access the correct set of devices in the initrd. Since we know which devices exist at install time, we can decide which ones we need.
The new 'homehost' concept should make it fairly easy for that special-case code to tell mdadm what to do.
Does that seem reasonable?
Yes. Another option which would work would be a "root=UUID-of-root" option or "md 0=UUID-of-md0,1=UUID-of-md1,..."
Gordon
