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Date:      Wed, 30 Jan 2002 19:46:26 -0600
From:      "Scott Gerhardt" <scott@gerhardt-it.com>
To:        "Brian T.Schellenberger" <bts@babbleon.org>
Cc:        <questions@FreeBSD.ORG>
Subject:   RE: Softupdates
Message-ID:  <KPEMLBLEMPMHGLJOCDEGCEIGDLAA.scott@gerhardt-it.com>
In-Reply-To: <20020131011543.10D3A4078@i8k.babbleon.org>

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   > > The write caching issue is more of an IDE-ATA issue.
   > > As far as I know write caching is not such an issue with
   > the newer SCSI
   > > drives that have Tagged Queueing Enabled (see dmesg from
   > one of my systems
   > > below).
   > >
   > > da0: 160.000MB/s transfers (80.000MHz, offset 63, 16bit),
   > Tagged Queueing
   > > Enabled
   > >
   > > I could be wrong, so correct me if I am.
   >
   > No, you are exactly correct.  I think that the ideal would
   > probably to be
   > have write caching disabled for ata (IDE) and enabled for SCSI.
   >
   > But I do wish that in marginal cases the defaults were more
   > conservative
   > myself.

I agree with your conservative approach.

Soft Updates + write caching on SCSI drives with Tagged Queueing Enabled
_should_ be quite safe....

High-end SCSI drives that cost 10x that of IDE should have some "smarts"
built into them.
The key is to make sure that you are aware of the appropriate firmware
upgrades (if any) for the drive models you are running.  I know this was an
issue with some of the IBM drives.

	- Scott




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