[SOLVED] Messed up with extending LVM with software RAID 5 config

Then for exchanging sdd1 against sdd :
mdadm --fail /dev/md0 /dev/sdd1
mdadm --remove /dev/md0 /dev/sdd1
dd if=/dev/zero of=/dev/sdd bs=1024k count=10240
mdadm --add /dev/md0 /dev/sdd
cat /proc/mdstat