From owner-freebsd-stable@FreeBSD.ORG Wed Sep 13 15:40:00 2006 Return-Path: X-Original-To: freebsd-stable@FreeBSD.org Delivered-To: freebsd-stable@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0C1E616A412 for ; Wed, 13 Sep 2006 15:40:00 +0000 (UTC) (envelope-from pjd@garage.freebsd.pl) Received: from mail.garage.freebsd.pl (arm132.internetdsl.tpnet.pl [83.17.198.132]) by mx1.FreeBSD.org (Postfix) with ESMTP id C20A043D4C for ; Wed, 13 Sep 2006 15:39:33 +0000 (GMT) (envelope-from pjd@garage.freebsd.pl) Received: by mail.garage.freebsd.pl (Postfix, from userid 65534) id 6D5E346DA5; Wed, 13 Sep 2006 17:39:32 +0200 (CEST) Received: from localhost (pjd.wheel.pl [10.0.1.1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.garage.freebsd.pl (Postfix) with ESMTP id 4001F48A26; Wed, 13 Sep 2006 17:39:21 +0200 (CEST) Date: Wed, 13 Sep 2006 17:39:09 +0200 From: Pawel Jakub Dawidek To: Teufel Message-ID: <20060913153909.GE70245@garage.freebsd.pl> References: <45066E19.2040405@kuehlbox.de> <20060913142329.GC70245@garage.freebsd.pl> <450823B1.2090809@kuehlbox.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="65ImJOski3p8EhYV" Content-Disposition: inline In-Reply-To: <450823B1.2090809@kuehlbox.de> X-PGP-Key-URL: http://people.freebsd.org/~pjd/pjd.asc X-OS: FreeBSD 7.0-CURRENT i386 User-Agent: mutt-ng/devel-r804 (FreeBSD) X-Spam-Checker-Version: SpamAssassin 3.0.4 (2005-06-05) on mail.garage.freebsd.pl X-Spam-Level: X-Spam-Status: No, score=-5.9 required=3.0 tests=ALL_TRUSTED,BAYES_00 autolearn=ham version=3.0.4 Cc: freebsd-stable@FreeBSD.org Subject: Re: gjournal and Softupdates X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 13 Sep 2006 15:40:00 -0000 --65ImJOski3p8EhYV Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Sep 13, 2006 at 05:28:49PM +0200, Teufel wrote: > Pawel Jakub Dawidek wrote: > >>>- todays desktop drives can lie about writing data. SoftUpdates relies > >>>on some assumptions about when the data is physically written to > >>>media, and those are not always valid today > >>> =20 > >>I think journaling relies on the same assumptions. > >> =20 > > > >Not gjournal, because it uses BIO_FLUSH I/O requests which flushes disk > >write cache when needed > so when the crash occur exactly when BIO_FLUSH is sent or while the > cache is flushing, there is still no corruption possbile? [...] That's right. One BIO_FLUSH is send to ensure the data are safely stored, and another one is send when metadata is updated to point at the last consistent journal. > [...] If so, this would be an advantage over SU, as=20 > it does surely not use the new introduced BIO_FLUSH. [...] Soft-updates doesn't handle disk write caches at all. > [...] In the other hand i've seen couple of other JFS that went corrupt f= or "no reason". I don't want to be paranoid, but i=20 > really want to be "sure" that the design is trustable. Of course a bug in file system (or gjournal) implementation is still possible and can lead to file system corruption, but such a bug can still corrupt file system in the way it will not be fixable by fsck. =46rom what I saw, file systems with journaling still enforce fsck every X reboots or on the next reboot after Y days of uptime, whatever comes first. --=20 Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! --65ImJOski3p8EhYV Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (FreeBSD) iD8DBQFFCCYdForvXbEpPzQRAhWdAJ9+Ow8IbGTYTCeDdGeqGBw4xXGLcgCbBhmu oSPG3J7sxUJRTZSi2qF58PE= =cTBj -----END PGP SIGNATURE----- --65ImJOski3p8EhYV--