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Date: Mon, 12 May 2008 07:58:48 -0600
From: Scott Long <scottl@samsco.org>
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To: Rong-en Fan <grafan@gmail.com>
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Cc: freebsd-scsi@freebsd.org
Subject: Re: default setting of WCE
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Rong-en Fan wrote:
> Hi,
> 
> I'm wondering what's the default of our da(4) regarding
> the WCE (write cache) bit. I see some of my disks has this
> bit on by default and some are off. I guess it depends on
> the capabilities returned by the underlying device when
> probing? In addition, on the same hardware, I found that
> Linux has write cache enabled by default... (yes, I have read
> da(4) and knows the pros/cons of enabling this).
> 

The 'da' driver leaves the WCE setting alone by default.  The
MPT driver does enable the write cache on SATA drives that it
finds on SAS controllers, but this is specific to this driver
and it happens unknown to the da driver.

Scott