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Date:      Fri, 15 Jul 2005 23:56:04 +0200
From:      Matthias Buelow <mkb@incubus.de>
To:        "Kevin Oberman" <oberman@es.net>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: dangerous situation with shutdown process 
Message-ID:  <200507152156.j6FLu4C5015051@drjekyll.mkbuelow.net>
In-Reply-To: Message from "Kevin Oberman" <oberman@es.net> of "Fri, 15 Jul 2005 14:03:19 PDT." <20050715210320.01E215D07@ptavv.es.net> 

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"Kevin Oberman" <oberman@es.net> writes:

>I believe that the Windows solution to this problem is to put a really,
>really long delay between when the system is finished syncing and when
>the power is turned off. This might be the best solution for FreeBSD, as
>well, but it will irritate people.

The Windows solution is, apparently, to disable and immediately
re-enable the writeback-cache around a barrier. This will ensure the
cache being written out to the platters, even if the drive ignores a
flush command.

Of course I don't know this for certain but have to rely on observations
that others have made. See, for example:

http://mail-index.netbsd.org/tech-kern/2002/12/09/0052.html

The long delay at shutdown would simply be a final safeguard in case
the drive also ignores disabling of the WC.

mkb.



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