In order to recover Linux software raid, and increase speed of RAID rebuilds, I found a nice howto at cyberciti.biz.
Warning !!! … these options are good for tweaking rebuilt process and may increase overall system load, high cpu and memory usage.
To increase speed, enter:
echo value > /proc/sys/dev/raid/speed_limit_min OR sysctl -w dev.raid.speed_limit_min=value
In this example, set it to 50000 K/Sec, enter:
# echo 120000 > /proc/sys/dev/raid/speed_limit_min