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Date:      Sat, 22 Sep 2001 18:20:52 -0700
From:      "Chad R. Larson" <chad@DCFinc.com>
To:        "Daniel O'Connor" <doconnor@gsoft.com.au>
Cc:        j mckitrick <jcm@FreeBSD-uk.eu.org>, freebsd-stable@FreeBSD.ORG, Nuno Teixeira <nuno.mailinglists@pt-quorum.com>, "David W. Chapman Jr." <dwcjr@inethouston.net>
Subject:   Re: hw.ata.wc && hw.ata.tags && softupdates short question
Message-ID:  <20010922182052.B16388@freeway.dcfinc.com>
In-Reply-To: <XFMail.20010921122607.doconnor@gsoft.com.au>; from doconnor@gsoft.com.au on Fri, Sep 21, 2001 at 12:26:07PM %2B0930
References:  <20010921035414.B75668@dogma.freebsd-uk.eu.org> <XFMail.20010921122607.doconnor@gsoft.com.au>

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On Fri, Sep 21, 2001 at 12:26:07PM +0930, Daniel O'Connor wrote:
> On 21-Sep-2001 j mckitrick wrote:
>>| Doesn't harware write cache usually write itself to disk before power 
>>| outage or even after?
>>  
>>  And wouldn't a laptop be safe with write caching?  At least if I keep the
>>  battery in?
> 
> Sure, but it is still a risk <shrugs>

Years ago, there was a main-frame drive manufacturer who used the
spindle motor as a generator in the case of a power failure.  The
kinetic energy in the spinning disk pack was converted to electricity,
so there would be enough energy to flush the cache to disk and then park
the heads.  I think it was Century.  You know, those drives that looked
like small washing machines and had removable disk packs?

I wonder if any of the current PC drive manufacturers do (or have
considered doing) the same thing?

	-crl
--
Chad R. Larson (CRL15)   602-953-1392   Brother, can you paradigm?
chad@dcfinc.com         chad@larsons.org          larson1@home.com
DCF, Inc. - 14623 North 49th Place, Scottsdale, Arizona 85254-2207

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