Booting with multiple RAID1 configs

[Titus von Boxberg]

> Here is what I did, and the subsequent effect:
> 
> (Remember, ad4 and ad6 (promise drives) make up the bootable ar0):
> 
> # after 2 brand new drives installed:
> 
> - atacontrol create RAID1 ad0 ad2
> ...at which point it said it was successful, and designated the new RAID
> config as ad1.
> 
> After reboot, the server comes up, identifies ad0, ad2, ad4 and ad6 as
> expected. Then it tries to load up the ar driver. It clearly says ar0
> has 2 disks, ad0 and ad2, and ad1 now has ad4 and ad6, which is
> backwards from how it should be.
> 
> Then it baffs with a mountroot error, and no manner of trying to point
> to any disk or array is successful. Mountroot errors 16 and 22 come up.
> 
> I pull the new drives back off the motherboard IDE connections, box goes
> back to exactly how it was before this mess started.

You might use loader(8) to set the root device ("rootdev" variable) 
explicitly to ar1s1a. Then you should also update fstab to reflect the 
numbering change.
I don't know of any way to change the ata numbering scheme.
Mainboard controllers always seem to be probed (and numbered)
first. I think there is no way to get your original raid
back to ar0 if you also use your mainboard controllers.

Cheers
Titus