[CentOS] question on software raid-1

I have a system that is RAID -1 configured as

/dev/md0 is /dev/hda1 /dev/hdb1 /dev/md1 is /dev/hdb3 /dev/hdb3

it seems as though /dev/hda has failed....

I have another disk (identical model) that I can replace hda with.

I know about the commands fdisk to repartion and raidhotadd /dev/md0 /dev/hda1 and raidhotadd /dev/md1 /dev/hda3 (to be ran after the system boots).

BUT... how do I now get the system to boot since hda is not there to boot... I can certainly execute the fdisk and raidhotadd after it boots... How do I get it to boot.

The hardware is a D865 intel motherboard with 2 seagate 120G drives.

Thanks,

Jerry