linux-kernel - Re: Raid not shutting down when disks are lost?

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Message-ID: <20091121170355.7540d169@mjolnir.ossman.eu>
Date:	Sat, 21 Nov 2009 17:03:55 +0100
From:	Pierre Ossman <pierre-list@...man.eu>
To:	neilb@...e.de
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Raid not shutting down when disks are lost?

Neil?

On Thu, 8 Oct 2009 16:39:52 +0200
Pierre Ossman <pierre-list@...man.eu> wrote:

> Today one RAID6 array I manage decided to lose four out of eight disks.
> Oddly enough, the array did not shut down but instead I got
> intermittent read and writer errors from the filesystem.
> 
> It's been some time since I had a failure of this magnitude, but I seem
> to recall that once the array lost too many disks, it would shut down
> and refuse to write a single byte. The nice effect of this was that if
> it was a temporary error, you could just reboot and the array would
> start nicely (albeit in degraded mode).
> 
> Has something changed? Is this perhaps an effect of using RAID6 (I used
> to run RAID5 arrays)? Or was I simply lucky the previous instances I've
> had?
> 
> Related, it would be nice if you could control how it handles lost
> disks. E.g. I'd like it to go read-only when it goes in to fully
> degraded mode. In case the last disk lost was only a temporary glitch,
> the array could be made to recover without a lengthy resync.
> 
> Rgds


-- 
     -- Pierre Ossman

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