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Date:      Sat, 23 Mar 2002 21:32:26 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Robert Watson <rwatson@freebsd.org>
Cc:        Willie Viljoen <will@laserfence.net>, freebsd-fs@freebsd.org, freebsd-bugs@freebsd.org
Subject:   Re: Soft update instability with heavy IO and offboard IDE controller
Message-ID:  <3C9D64EA.BBE84A89@mindspring.com>
References:  <Pine.NEB.3.96L.1020323182807.47668I-100000@fledge.watson.org>

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Robert Watson wrote:
> On Sat, 23 Mar 2002, Terry Lambert wrote:
> > Disable write caching on the drives.  THis is a FAQ.
> 
> Hmm.  I thought the wc bit should only affect this sort of scenario in the
> event that the system was actually powered off; otherwise, the hard disk
> can still flush to disk gradually as it.  From the description, it seems
> the system panics, but power is never removed from the drives.  That said,
> I wouldn't be surprised if the problem goes away on the basis that this
> will substantially change system behavior for performance reasons, hiding
> whatever subtle bug it is :-).

The drive lies about commiting data to stable storage.  This
blows away all the hard work soft updates does trying to
ensure ordering.

-- Terry

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