From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Ceuleers <jan.ceuleers@computer.org>
Subject: Re: Spares not added upon reboot after distro upgrade
Date: Wed, 22 Aug 2012 13:26:03 +0200
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On 08/19/2012 09:42 AM, Jan Ceuleers wrote:
...

> For the first time ever I tried mdadm's incremental mode. So before
> issuing the above two commands I tried the following;
> 
> root@zotac:~# mdadm -I /dev/sde2
> mdadm: failed to add /dev/sde2 to /dev/md0: Invalid argument.

I have now straced this, and here are the offending lines:

ioctl(4, 0x40140921, 0x7fff4bda3858)    = -1 EINVAL (Invalid argument)
write(2, "mdadm: failed to add /dev/sde2 t"..., 62mdadm: failed to add
/dev/sde2 to /dev/md0: Invalid argument.

fd 4 is /dev/md0

How does one decode the ioctl call?

Thanks, Jan