From owner-freebsd-scsi  Sat Oct  3 00:36:23 1998
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From: Wilko Bulte <wilko@yedi.iaf.nl>
Message-Id: <199810022254.AAA04758@yedi.iaf.nl>
Subject: Re: filesystem safety and SCSI disk write caching
In-Reply-To: <199810021929.NAA11650@pluto.plutotech.com> from "Justin T. Gibbs" at "Oct 2, 98 01:23:27 pm"
To: gibbs@plutotech.com (Justin T. Gibbs)
Date: Sat, 3 Oct 1998 00:54:44 +0200 (CEST)
Cc: Don.Lewis@tsc.tdk.com, freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG
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As Justin T. Gibbs wrote...
> >Yuck. Write caching on disks is evil. I've discussed this kind of
> >thing at great length with the disk gurus at work. There is consensus:
> >write caching is not to be trusted, there are even firmware incarnations
> >out there that get confused by a SCSI bus reset and loose track of what
> >they have cached. Admittedly this is junk firmware, but it seems to
> >happen.
> 
> Your statement doesn't seem to be "write caching is inherently evil",
> but "there are many drives with bogus firmware where write caching is
> evil".  There is a big difference.  If you have a sane device and a

True, there is a big difference alright. But the problem is that is
not easy for an average user to find out how well behaved a disk's fw
actuall is.

> UPS, write caching is not evil at all.

Right. I for one opt for security over a (small ?) performance gain.

Wilko
_     ______________________________________________________________________
 |   / o / /  _  Bulte 				  email: wilko@yedi.iaf.nl 
 |/|/ / / /( (_) Arnhem, The Netherlands          WWW  : http://www.tcja.nl
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