- Ahh OK now I see why I was confused. The originally posted partition map uses cylinders as units, not LBA. I missed that. Cylinder 1 is the same as LBA 63. And that is sufficiently large for a GRUB legacy stage 2. - OK this is screwy. Partitions 1 and 3 on both drives have the same number of sectors, but partitions 2 differ: /dev/hde2 401,625 975,691,709 975,290,085 fd Linux raid autodetect /dev/hdg2 401,625 1,952,491,904 1,952,090,280 fd Linux raid autodetect That can't work as these are two partitions meant to form /dev/md2 and need to be the same size. - Also, 401625 is not 8 sector aligned. So it's a double whammy and since it has to be repartitioned anyway you might as well fix the alignment also. First off fail+remove hdg2 (you need to confirm I've got the devices and commands right here): mdadm --manage /dev/md2 -f /dev/hdg2 -r /dev/hdg2 mdadm --zero-superblock /dev/hdg2 Using fdisk delete hdg2, then make a new primary partition (partition 2) and hopefully figure out how to get it to do LBA rather than CHS entry; or use parted which can but it's UI is totally unlike fdisk. The start sector for hdg2 should be 401623 which is 8 sector aligned, and the end value should be 975691717 in order to make it the same as hde2. And change the type to 0xfd. Now you probably have to reboot because the partition map has changed, I'm not sure if partprobe exists on CentOS5, could be worth a shot though and see if the kernel gets the new partition map. Check with blkid. And then finally add the "new" device. mdadm --managed /dev/md2 -a /dev/hdg2 And now it should be resyncing... cat /proc/mdstat Something like that. Proof read it! --- Chris Murphy