From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: Inoperative array shown as "active"
Date: Sat, 14 Sep 2013 15:59:12 +1000
Message-ID: <20130914155912.5ba135d9@notabene.brown>
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To: Ian Pilcher <arequipeno@gmail.com>
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On Sat, 14 Sep 2013 00:39:20 -0500 Ian Pilcher <arequipeno@gmail.com> wrote:

> I'm in the process of writing a program to monitor various aspects of
> my NAS.  As part of this effort, I've been simulating RAID disk failures
> in a VM, and I noticed something that seems very odd.
>=20
> Namely, when a sufficient number of disks has been removed from a RAID-5
> or RAID-6 array to make it inoperable, the array is still shown as
> "active" in /proc/mdstat and "clean" in the sysfs array_state file.  For
> example:
>=20
> md0 : active raid5 sde[3](F) sdd[2] sdc[1](F) sdb[0]
>       6286848 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/2] [U_=
U_]
>=20
> (mdadm does show the state as "clean, FAILED".)
>=20
> Is this the expected behavior?

Yes.

>=20
> AFAICT, this means that there is no single item in either /proc/mdstat
> or sysfs that indicates that an array such as the example above has
> failed.  My program will have to parse the RAID level, calculated the
> number of failed members (if any), and determine whether that RAID level
> can survive that number of failures.  Is this correct?

Yes.

>=20
> Anything I'm missing?

mdadm already does this for you. "mdadm --detail /dev/md0".

NeilBrown

>=20
> Thanks!
>=20


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