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Date:      Sat, 26 May 2001 15:10:51 -0700 (PDT)
From:      Matt Dillon <dillon@earth.backplane.com>
To:        Jean-Sebastien ROY <jean-sebastien.roy@wanadoo.fr>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: Updated Tuning man page on web
Message-ID:  <200105262210.f4QMApr00990@earth.backplane.com>
References:  <200105260720.f4Q7KsG48718@earth.backplane.com> <jean-sebastien.roy-224357.12010726052001@durandal.root>

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:
:In article <200105260720.f4Q7KsG48718@earth.backplane.com>,
: dillon@earth.backplane.com (Matt Dillon) wrote:
:
:> http://apollo.backplane.com/FreeBSD/tuning.html
:
:In this very useful man page, you wrote :
:
:> There is a new experimental feature for IDE hard drives
:> called hw.ata.tags (you also set this in the boot- loader)
:> which allows write caching to be safely turned on.
:
:Does this means hw.ata.wc must/should be turned on ? I thought turning 
:on hw.ata.tags would enable write caching even with hw.ata.wc off.

    If you turn on tags and the drive supports them, hw.ata.wc is 
    ignored and write caching is turned on.  So to support tags you
    just turn hw.ata.tags on and leave hw.ata.wc off.

					-Matt

:> As of this writing only IBM DPTA and DTLA drives support the feature.
:
:I think the ata driver is checking each drive to see if it's a supported 
:drive (on a supported controller (!= Promise)), so hw.ata.tags can be 
:turned on even if other drives are unsupported (and hw.ata.wc should not 
:be enabled to prevent write caching to be turned on on drives that do no 
:support ata.tags).
:
:js
:


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