Mdadm – Increase Resync speed when rebuilding array

root@donkey:/data# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md127 : active raid6 sdf[4] sde[3] sdd[2] sdb[0] sdc[1]
5860148736 blocks super 1.2 level 6, 512k chunk, algorithm 2 [5/5] [UUUUU]
[>………………..] resync = 3.0% (58704384/1953382912) finish=30575.8min speed=1032K/sec

unused devices: <none>
root@donkey:/data# cat /proc/sys/dev/raid/speed_limit_min
1000
root@donkey:/data# echo 50000 > /proc/sys/dev/raid/speed_limit_min
root@donkey:/data# cat /proc/sys/dev/raid/speed_limit_min
50000
root@donkey:/data# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md127 : active raid6 sdf[4] sde[3] sdd[2] sdb[0] sdc[1]
5860148736 blocks super 1.2 level 6, 512k chunk, algorithm 2 [5/5] [UUUUU]
[>………………..] resync = 3.0% (59043984/1953382912) finish=3677.4min speed=8584K/sec