Software RAID - making the spare bootable

[Matt Brock]

Hi there.

I've been using Yellow Dog Linux on Apple Xserve G5s for a couple of  
years now and it does a great job. Recently I decided to rebuild one  
with software RAID to get disk redundancy. I did all of this through  
the installer. The server has three disks, so I set them up as RAID 1  
with a spare.

This has all gone very successfully apart from one detail. The two  
disks in the RAID set are bootable, i.e. I can remove either of those  
disks and the machine will still boot as normal. That's fine so far.  
Then I permanently removed the first disk and brought the spare third  
disk into the RAID set instead. Once the RAID set is then fully  
rebuilt I can boot off the original second disk, but the third disk  
which was previously the spare disk is not bootable. It gets to the  
first yaboot stage, and then the blue icon which represents OpenBoot  
failing to find a boot disk appears superimposed over the yaboot  
screen. That process just loops over and over again and never boots.

I've tried using ybin to make the Apple boot partition bootable with  
the correct yaboot config, but that didn't help. I've tried dd-ing the  
entire second disk onto the third disk then zeroing the RAID  
superblocks, and that didn't work. I've tried resetting the NVRAM and  
that made no difference. I'm sure it's not a hardware problem with the  
disk because I've tried this twice now with the disks in different  
slots each time, and it's always the spare disk which has the boot  
problem even though that's a different physical disk each time.

I hope there's someone out there who can help because I'm tearing my  
hair out over this. I can't see what else would be needed to make the  
third disk bootable... yet there must be something! Without getting  
this working the full redundancy I'd hoped for can't be achieved,  
which would be extremely frustrating.

Cheers,

Matt.