Build my Linux Software RAID5 at home

It is great.

I create raid5 with 3 disk
then add one more disk by

mdadm --manage /dev/mdX --add /dev/sd?1
mdadm --grow /dev/mdX --raid-devices=4 (original is 3)

This will reshape at the back. Very slow but find the below to speed up

In Fedora 7, original value
cat /proc/sys/dev/raid/speed_limit_min ==> 1000
echo 100000 > /proc/sys/dev/raid/speed_limit_min