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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
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up vote 1 down vote accepted

You cannot grow a RAID1+0 (it's not supported by mdadm).

From mdadm manpage:


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So I cannot do anything else than keep current situation or restart from beginning, correct? :( –  Marco Sep 4 '13 at 9:00
on very recent kernels (>3.0) you may be able to convert raid10 to raid0, but it's a risky business. Maybe someone can chime in on this. –  Cubiq Sep 4 '13 at 9:03
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