issue with mdadm and mirroring drives

[Joey L <mjh2000@gmail.com>]

I have a raid 1 mdadm setup.
I have devices sda and sdb with 2 partitions on each - sda1 and sda2
on the other drive i have sdb1 and sdb2.

Partition sda1 is the root partition and sda2 is the swap partition.

My sda failed yesterday and now i am running in sdb only.

When i put the drive sda into the system to add it back to the md0 -
the system keeps booting from it and refuses to boot from the good sdb
drive.

What can i do to stop this from happening - I have no other system to
plug this drive into to zero out the drive.

Also if I am able to get over this issue - do i have to do other
procedures to this drive? what are they ??? I think i have to do the
following:

mdadm --manage /dev/md0 --remove /dev/sdb1

mdadm --manage /dev/md0 --fail /dev/sdb1

sfdisk -d /dev/sda | sfdisk /dev/sdb

mdadm --manage /dev/md0 --add /dev/sdb1


I am thinking that I need to do something with grub or do some kind of
update so the server can boot of the good drive that I have working
now - but do not know what it is.

thanks
mjh