From owner-freebsd-fs Sun Oct 18 12:29:30 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id MAA27376 for freebsd-fs-outgoing; Sun, 18 Oct 1998 12:29:30 -0700 (PDT) (envelope-from owner-freebsd-fs@FreeBSD.ORG) Received: from smtp03.primenet.com (smtp03.primenet.com [206.165.6.133]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id MAA27365; Sun, 18 Oct 1998 12:29:28 -0700 (PDT) (envelope-from tlambert@usr06.primenet.com) Received: (from daemon@localhost) by smtp03.primenet.com (8.8.8/8.8.8) id MAA24841; Sun, 18 Oct 1998 12:29:06 -0700 (MST) Received: from usr06.primenet.com(206.165.6.206) via SMTP by smtp03.primenet.com, id smtpd024822; Sun Oct 18 12:28:59 1998 Received: (from tlambert@localhost) by usr06.primenet.com (8.8.5/8.8.5) id MAA19832; Sun, 18 Oct 1998 12:28:58 -0700 (MST) From: Terry Lambert Message-Id: <199810181928.MAA19832@usr06.primenet.com> Subject: Re: filesystem safety and SCSI disk write caching To: julian@whistle.com (Julian Elischer) Date: Sun, 18 Oct 1998 19:28:58 +0000 (GMT) Cc: guido@gvr.org, tlambert@primenet.com, dkelly@hiwaay.net, freebsd-fs@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG In-Reply-To: from "Julian Elischer" at Oct 17, 98 06:59:41 pm X-Mailer: ELM [version 2.4 PL25] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-fs@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org > > I always thought a drive will always be able to flush its write cache > > to disk, even when power fails. > > no, > That's a myth. Actually, there are a number of drives which used to be manufactured, which did this. I don't think anyone is manufacturing them any more, but I know that at least one 7200 RPM IBM SCSI drive did this, and I have the spec sheets (somewhere) for a quantum that would so this, so long as the unwritten data was only a single track. Perhaps they realized that the mpst likely event after a power fluctuation was a bus reset, and figured "why bother?". Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message