Alt-f Slow RAID Resync
When I was attempting to build a new RAID-1 array on a DSM-323, I was getting brutal performance. Tweaking speed_limit_min helped significantly.
[root@localhost]# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sda2[1] sdb2[0]
1464611576 blocks super 1.0 [2/2] [UU]
[>....................] resync = 0.3% (5201664/1464611576) finish=202400.3min speed=120K/sec
bitmap: 11/11 pages [44KB], 65536KB chunk
finish=202400.3min is 140 days to complete the sync!
Changing the following settings in /proc sped things up significantly
sudo echo 100000 > /proc/sys/dev/raid/speed_limit_min
sudo echo 400000 > /proc/sys/dev/raid/speed_limit_max
[root@localhost]# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4]
md0 : active raid1 sda2[1] sdb2[0]
1464611576 blocks super 1.0 [2/2] [UU]
[=====>...............] resync = 28.3% (415173632/1464611576) finish=265.8min speed=65792K/sec
bitmap: 8/11 pages [32KB], 65536KB chunk