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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!newsroom.utas.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!paladin.american.edu!gatech!newsfeed.internetmci.com!in2.uu.net!newsfeed.pitt.edu!neurocog.lrdc.pitt.edu!hahn From: hahn@neurocog.lrdc.pitt.edu (Mark Hahn) Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system Subject: Re: async or sync metadata [was: FreeBSD v. Linux] Followup-To: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system Date: 15 Feb 1996 01:17:54 GMT Organization: University of Pittsburgh Lines: 28 Message-ID: <4fu1k2$6su@usenet.srv.cis.pitt.edu> References: <4er9hp$5ng@orb.direct.ca> <4f9skh$2og@dyson.iquest.net> <DMI5Mt.768@pe1chl.ampr.org> <4fi6gq$3tr@dyson.iquest.net> <4fjodc$o8j@venger.snds.com> <4fopq4$ahl@park.uvsc.edu> NNTP-Posting-Host: neurocog.lrdc.pitt.edu Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:14277 comp.os.linux.development.system:17901 > ] 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). safety implies stable storage, when both data and its meta are safely on some media. logs are a way to make it much less expensive to achieve stability. > You don't know what you are talking about. I have referenced > both papers and mathematical models for file system recovery > to refute this specious claim. The only thing I have seen from > the opposition is bind assertion. Blind assertion is not proof. neither is an appeal to authority. the question is how much async/async (meta/data) is more dangerous or unappealing than async/sync. this is largely subjective, hinging upon how you feel about the idea of random data winding up in files that fsck clean. corruption is possible in either case. if you make log entries when any async block becomes stable, this can hardly be called async. regards, mark hahn. -- operator may differ from spokesperson. hahn@neurocog.lrdc.pitt.edu http://neurocog.lrdc.pitt.edu/~hahn/