Date: Wed, 13 Sep 2006 17:39:09 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Teufel <bsd@kuehlbox.de> Cc: freebsd-stable@FreeBSD.org Subject: Re: gjournal and Softupdates Message-ID: <20060913153909.GE70245@garage.freebsd.pl> In-Reply-To: <450823B1.2090809@kuehlbox.de> References: <45066E19.2040405@kuehlbox.de> <ee5vat$fcb$1@sea.gmane.org> <ygfirjto0z2.fsf@dominion.borderworlds.dk> <20060913142329.GC70245@garage.freebsd.pl> <450823B1.2090809@kuehlbox.de>
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--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--
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