I'm pretty new to RAID, so please forgive my silly question.
I have an Ubuntu Server 12.04 x64
installed on a pc having 4 hdds.
During RAID setup I selected RAID10 and (my ignorance) choose 2 active hdds and 2 spare hdds. I'm pretty sure it's not the optimal configuration and probably I should have selected 4 active hdds.
Running cat /proc/mdstat
I get
md1 : active raid10 sdb2[1] sdd2[3](S) sdc2[2](S) sda2[0]
948736 blocks super 1.2 2 near-copies [2/2] [UU]
md0 : active raid10 sdb1[1] sdd1[3](S) sdc1[2](S) sda1[0]
311619072 blocks super 1.2 2 near-copies [2/2] [UU]
unused devices: <none>
Is there a way I can convert spare disks to active disks?
I tried using mdadm --grow /dev/md1 --raid-devices=4
, but got this answer
mdadm: RAID10 can only be changed to RAID0