From owner-freebsd-current@FreeBSD.ORG  Tue Aug  2 17:49:01 2005
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To: Wilko Bulte <wb@freebie.xs4all.nl>
In-reply-to: Your message of "Tue, 02 Aug 2005 18:00:45 +0200."
	<20050802160045.GA61854@freebie.xs4all.nl> 
Date: Tue, 02 Aug 2005 10:48:59 -0700
From: "Kevin Oberman" <oberman@es.net>
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Cc: Colin King <ring_06@m202.net>, Scot Hetzel <swhetzel@gmail.com>,
	Justin Finkelstein <justin@redwiredesign.com>, freebsd-current@freebsd.org
Subject: Re: Hot-swap SATA and atacontrol 
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> Date: Tue, 2 Aug 2005 18:00:45 +0200
> From: Wilko Bulte <wb@freebie.xs4all.nl>
> Sender: owner-freebsd-current@freebsd.org
> 
> On Tue, Aug 02, 2005 at 10:44:07AM -0500, Scot Hetzel wrote..
> > On 8/2/05, Justin Finkelstein <justin@redwiredesign.com> wrote:
> > > I might be being a little dense, but what do you mean by sync?
> > > 
> > before you unmount the drive, type:
> > 
> > sync
> > sync
> > sync
> > 
> > Then unmount the drive, and remove it.
> 
> Unmount does not return until the buffers have been synced anyway,
> so this does not buy you anything.
> 
> The ancient form is more like:
> 
> sync;sync;sync;<halt button on your PDP/11 frontpanel>

Not really. The PDP-11 (and early VAX) invocation was:
sync
sync
sync
<Hit halt switch>

There was a real difference between that and sync;sync;sync. Either was
usually effective, but the delay to enter actual separate commands was
required for real safety. (Unix file systems were really pretty unstable
back then. fsck was the norm on many reboots, even if you THOUGHT that
they had been safely dismounted.)
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net			Phone: +1 510 486-8634