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Date:      Mon, 23 Aug 2004 22:38:55 +0200
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Dan Nelson <dnelson@allantgroup.com>
Cc:        freebsd-arch@freebsd.org
Subject:   Re: Mounting root...
Message-ID:  <20040823203855.GV30151@darkness.comp.waw.pl>
In-Reply-To: <20040823200157.GA36920@dan.emsphone.com>
References:  <20040823073559.GP30151@darkness.comp.waw.pl> <200408231146.12972.jhb@FreeBSD.org> <20040823190541.GS30151@darkness.comp.waw.pl> <20040823200157.GA36920@dan.emsphone.com>

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On Mon, Aug 23, 2004 at 03:01:57PM -0500, Dan Nelson wrote:
+> How about maybe blocking on the initial access to a degraded mirror for
+> 5 (just a guess) seconds to see if the other half shows up?  If it
+> doesn't, assume it's never showing up and use what you have.  When the
+> other disk arrives, sync your changes over to it. [...]

I'm waiting for few seconds for the rest of components now, but mounting
root routine doesn't wait for me.
And I'm not going to create provider without given a chance to the rest
components to show up, because I can end up with mirror started on stale
component, because a fresh one showed up with some delay.

+> If geom_mirror keeps
+> an on-disk bitmap of dirty blocks for fast resyncs, copy your data over
+> the other mirror's dirty blocks.  You'll lose whatever changes were
+> made to that disk, but at least the filesystem will be consistent.

Geom_mirror doesn't keep bitmap with dirty blocks in metadata, this will
probably slowdown things a lot.

Synchronization in geom_mirror is based on 'syncid'. Basically one can
set kern.geom.mirror.timeout to 0 and there will be no need to rebuild
if there will be no write to the mirror...

--=20
Pawel Jakub Dawidek                       http://www.FreeBSD.org
pjd@FreeBSD.org                           http://garage.freebsd.pl
FreeBSD committer                         Am I Evil? Yes, I Am!

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