mdX and sdXX are used to save you from copy-paste troubles

To stop recovery mark drive as "fault"

mdadm /dev/mdX -f /dev/sdXX

Speed-up recovery

sudo echo 100000 > /proc/sys/dev/raid/speed_limit_min
sudo echo 400000 > /proc/sys/dev/raid/speed_limit_max
mdadm --grow --bitmap=internal /dev/mdX

Re-add drive

mdadm /dev/mdX -r /dev/sdXX
mdadm /dev/mdX -a /dev/sdXX

Watch your recovery

watch /cat/prod/mdstat

Once array rebuild or fully synced, disable bitmaps

mdadm --grow --bitmap=none /dev/mdX