Date: Thu, 29 Nov 2001 00:25:06 +0100
From: Frank de Lange <lkml-frank@unternet.org>
To: linux-kernel@vger.kernel.org
Subject: Re: Journaling pointless with today's hard disks?
Message-ID: <20011129002506.A1013@unternet.org>
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On Mon, 26 Nov 2001, Richard B. Johnson wrote:

> It isn't that easy! Any kind of power storage within the drive would
> have to be isolated with diodes so that it doesn't try to run your
> motherboard as well as the drive. This means that +5 volt logic supply
> would now be 5.0 - 0.6 = 4.4 volts at the drive, well below the design
> voltage. Use of a Schottky diode (0.34 volts) would help somewhat, but you
> have now narrowed the normal power design-margin by 90 percent, not good.

Another interesting possibility would be to use the momentum of the spinning
platters and motor assembly to power the drive electronics, simply by using the
motor as a generator. When power fails during a write, use the current
generated by the motor to finish the write.

Just a wild idea...

Cheers//Frank
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