Bug#495580: mdadm: 4 disk raid10 with 1 active and 3 spare possible

[martin f krafft]

also sprach Felix Zielcke <fzielcke at z-51.de> [2008.08.19.0829 +0200]:
> fz-vm:~# mdadm -f /dev/md0 /dev/sdc1 
> mdadm: set /dev/sdc1 faulty in /dev/md0
> fz-vm:~# mdadm -r /dev/md0 /dev/sdc1 
> mdadm: hot removed /dev/sdc1
> fz-vm:~# mdadm -a /dev/md0 /dev/sdc1 
> mdadm: re-added /dev/sdc1
> fz-vm:~# mdadm -f /dev/md0 /dev/sdd1 
> mdadm: set /dev/sdd1 faulty in /dev/md0
> fz-vm:~# mdadm -r /dev/md0 /dev/sdd1 
> mdadm: hot removed /dev/sdd1

Unless you waited for /dev/sdc1 to resync, removing /dev/sdd1 will
basically destroy the array. Not much one can do about that.

Anyway, I think that's the problem: when you (re-)add a disk to an
array, it becomes a spare until it synchronised. If you wait for the
synchronisation between each add/remove step, you should never see
more than 1 spare.

-- 
 .''`.   martin f. krafft <madduck at debian.org>
: :'  :  proud Debian developer, author, administrator, and user
`. `'`   http://people.debian.org/~madduck - http://debiansystem.info
  `-  Debian - when you have better things to do than fixing systems
 
"man sagt nicht 'nichts!', man sagt dafür 'jenseits' oder 'gott'."
                                                 - friedrich nietzsche
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