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Date:      Sun, 16 Jan 2000 19:05:20 +0530
From:      Greg Lehey <grog@lemis.com>
To:        Tyler Barnett <tbarnett@stdio.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: CCD recovery questions
Message-ID:  <20000116190520.P3413@mojave.worldwide.lemis.com>
In-Reply-To: <200001130307.WAA78568@heathers.stdio.com>; from tbarnett@stdio.com on Wed, Jan 12, 2000 at 10:07:09PM -0500
References:  <200001130307.WAA78568@heathers.stdio.com>

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On Wednesday, 12 January 2000 at 22:07:09 -0500, Tyler Barnett wrote:
> I'm running 3.3 stable, and created a 12GB CCD mirror from 2
> identical disk drives.
>
> To test the scenario of one of them failing, I shutdown the system
> and unplugged one.  During boot the ccd driver refused to config it.
> The system dropped into single-user mode for an fsck.

Fun, isn't it?  This is a "feature" of ccd.  Vinum would handle this
situation correctrly.

> I tried removing the "unplugged" disk drive from the ccd.conf line,
> effectively meaning that ccd0 had only 1 disk drive (the working
> one).  It didn't work, still wanted to fsck.

That should have worked.  You'll still need to reconfigure, which
implies rebooting.  Possibly you told ccd that it still had a mirror.

> I still haven't brought myself to test the scenario of unplugging a
> drive "hot", and seeing what happens :-)

You'll crash the ccd.

> I'm not getting a warm fuzzy feeling about this.  Unless I can
> figure out how to separate the ccd mirror, or run on 1 drive alone
> for a short period of time, I think I just statistically have halved
> the MTBF of either drive.  And recovery from a drive failure as such
> seems impossible.

Agreed.

> BTW, I've used Solstice on Solaris (please no flames) and it has
> saved my bacon on a mirror failure.  Otherwise, the FBSD ccd works
> just fine.  I just want to know what to do when it doesn't.

Move to vinum.  I don't see any advantage in ccd any more.  Check out
vinum(4), vinum(8) and http://www.lemis.com/vinum.html.

Greg
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