Remove a Disk
mdadm /dev/md1 --fail /dev/sda1
mdadm /dev/md1 --remove /dev/sda1
Stop RAID
mdadm --stop /dev/md1
Start RAID
mdadm --assemble --scan
Prepare New Disk (copy partition layout)
sfdisk -d /dev/sda | sfdisk /dev/sdb
Add New Disk
mdadm --manage /dev/md1 --add /dev/sda1
View RAID Status
cat /proc/mdstat
Further Reading
www.iceteks.com/articles.php/linuxmdadmraid/3
www.mrbuckykat.com/mdadm-cheat-sheet
www.linux-sxs.org/storage/fedora2ubuntu.html
www.cyberciti.biz/faq/warning-duplicate-vg-name-server01-error/
www.ducea.com/2009/03/08/mdadm-cheat-sheet/