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Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!nntp.coast.net!howland.reston.ans.net!nntp.crl.com!pacbell.com!amdahl.com!amd!netcomsv!uu4news.netcom.com!netcomsv!uu3news.netcom.com!ix.netcom.com!netcom.com!jlemon From: jlemon@netcom.com (Jonathan Lemon) Subject: Re: async or sync metadata [was: FreeBSD v. Linux] Message-ID: <jlemonDMMDq5.1yF@netcom.com> Organization: NETCOM On-line Communication Services (408 261-4700 guest) References: <4er9hp$5ng@orb.direct.ca> <DMI5Mt.768@pe1chl.ampr.org> <4fi6gq$3tr@dyson.iquest.net> <4fjodc$o8j@venger.snds.com> Date: Sun, 11 Feb 1996 16:27:41 GMT Lines: 24 Sender: jlemon@netcom22.netcom.com Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:13619 comp.os.linux.development.system:17125 In article <4fjodc$o8j@venger.snds.com>, Michael Griffith <grif@hill.ucr.edu> wrote: >|In article <DMI5Mt.768@pe1chl.ampr.org>, >|Rob Janssen <pe1chl@wab-tis.rabobank.nl> wrote: >|>It seems to be very hard to get this misconception out of the BSD people's >|>heads... >|>Sync metadata writes may seem to improve things, but actually it just >|>causes your fsck's to return no errors while the files are still >|>corrupted. Not necessarily better. > >Very hard indeed. Here it is one more time: > > sync metadata with async data is not just slower, > it is LESS SAFE. This behavour should not be the default > on any reasonable system. If you want real safety, > then both data and meta need to be synchronous (i.e. no > buffer cache for writes). This real safety comes with > an huge performance hit (as in MSDOS). Um, Michael, Rob? Sync metadata just insures that the _filesystem_ is always in a consistent state, not the data itself. It is safer in the sense that you don't lose the entire filesystem, not that you don't lose data. -- Jonathan