software raid recovery
1. If /dev/sdb is faild then copy partions from /dev/sda to /dev/sdb
sfdisk -d /dev/sda | sfdisk /dev/sdb

2. Add partions to raid
a. find which partition are on which md

mdadm --brief --detail --verbose /dev/md0
ARRAY /dev/md0 level=raid1 num-devices=2 UUID=a2c87b55:29d205b1:6bd0e33e:52e9ad5d  devices=/dev/sda1

3. add same partition to md
mdadm --manage /dev/md0 --add /dev/sdb1
mdadm: added /dev/sdb1