Just to add - I've just had a 2TB sda disk fail which was part of a RAID 1 mirror to sdb.

The disks were connected to connected to a AMD SB710 controller and the server was running Centos 5.7

I did have problems getting the system to boot from sdb ( fixed by re-installing grub to sdb ) but I'd thought I'd report I was able to successfully disconnect the failed sda and hot-plug the new drive in, with it showing up as a 'blank' disk with fdisk -l.

Copying the partition table from sdb to sda ( sfdisk as above plus using the --force as noted due to Centos ) I could then add back in the partitions to the different arrays as detailed in the and watch the disks rebuild. The four 2TB disk RAID5 array took around 6 hours to rebuild.

Have to also got to say, this is an excellent how-to.