Rebuild Linux software RAID

mdadm -r /dev/md0 /dev/sdb1
 
dd if=/dev/sda of=/dev/sdb bs=512 count=1
 
echo 1 > /sys/block/sdb/device/rescan
or reboot
 
mdadm -a /dev/md0 /dev/sdb1
 
# Links
http://www.cyberciti.biz/faq/debian-ubuntu-reload-partition-table/
http://linuxwiki.de/mdadm