Using the mkinitrd patch that I posted before, the result was that
mdadm did try to bring up all raid devices but, because the raid456
module was not loaded in initrd, the raid devices were left inactive.
Then, when rc.sysinit tried to bring them up with mdadm -A -s, that
did nothing to the inactive devices, since they didn't have to be
assembled. Adding --run didn't help.
My current work-around is to add raid456 to initrd, but that's ugly.
Scanning /proc/mdstat for inactive devices in rc.sysinit and doing
mdadm --run on them is feasible, but it looks ugly and error-prone.
Would it be reasonable to change mdadm so as to, erhm, disassemble ;-)
the raid devices it tried to bring up but that, for whatever reason,
it couldn't activate? (say, missing module, not enough members,