Re:

[NeilBrown <neilb@suse.de>]

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On Wed, 26 Nov 2014 12:38:44 -0600 Travis Williams <travis@euppc.com> wrote:

> Hello all,
> 
> I feel as though I must be missing something that I have had no luck
> finding all morning.
> 
> When setting up arrays with spares in a spare-group, I'm having no
> luck finding a way to get that information from mdadm or mdstat. This
> becomes an issue when trying to write out configs and the like, or
> simply trying to get a feel for how arrays are setup on a system.
> 
> Many tutorials/documentation/etc etc list using `mdadm --scan --detail
> >> /etc/mdadm/mdadm.conf` as a way to write out the running config for
> initialization at reboot.  There is never any of the spare-group
> information listed in that output. Is there another way to see what
> spare-group is included in a currently running array?
> 
> It also isn't listed in `mdadm --scan`, or by `cat /proc/mdstat`
> 
> I've primarily noticed this with Debian 7, with mdadm v3.2.5 - 18th
> May 2012. kernel 3.2.0-4.
> 
> When I modify the mdadm.conf myself and add the 'spare-group' setting
> myself, the arrays work as expected, but I haven't been able to find a
> way to KNOW that they are currently running that way without failing
> drives out to see. This nearly burned me after a restart in one
> instance that I caught out of dumb luck before anything of value was
> lost.
> 

mdadm.conf is the primary  location for spare-group information.
When "mdadm --monitor" is run, it reads that file and uses that information.
If you change the spare-group information in mdadm.conf, it would make sense
to restart "mdadm --monitor" so that it uses the updated information.

mdadm --scan --detail >> /etc/mdadm.conf

was only even meant to be a starting point - a guide.  You are still
responsible for your mdadm.conf file.

NeilBrown

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