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Date:      Wed, 28 Nov 2001 00:55:09 +0100
From:      "Anthony Atkielski" <anthony@freebie.atkielski.com>
To:        <denorris@bellsouth.net>, <freebsd-questions@FreeBSD.ORG>
Subject:   Re: ATA drive manufacturers and write caching
Message-ID:  <017901c1779e$f30a6f50$0a00000a@atkielski.com>
References:  <200111272330.fARNUHh31082@visar.norris-net.com>

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Normally drives that "lie" should have some sort of provision for writing the
data to the disk or at least retaining it even in the event of power failure.
This would be something like a battery backup for memory in the internal cache
or something like that.  The data stays there indefinitely, and when the power
returns, the write to disk is completed.

I know that this can still cause problems, in some cases.  I know of at least
one case in which software attempted to _disable_ on-board write caching on a
disk drive, and hashed the geometry of the drive--the damage done was so severe
that the drive had to be sent back to the factory, and generally all data was
lost, anyway.

----- Original Message -----
From: "Derrick Norris" <denorris@bellsouth.net>
To: <freebsd-questions@FreeBSD.ORG>
Sent: Wednesday, November 28, 2001 00:30
Subject: ATA drive manufacturers and write caching


> I have read documentation and followed several discussions about the
> performance benefits of enabling write caching on ATA hard drives vs.
> the inherent risks.  Saw several statements to the effect that some
> drives "lie" about whether/when the data in their cache was actually
> written to the platter, thus potentially causing problems.
>
> Does anyone have information about particular drive manufacturers or
> models that exhibit this behavior, or was it just a general statement
> about ATA drives?
>
> Thanks,
> Derrick
>
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