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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!nntp.coast.net!howland.reston.ans.net!newsfeed.internetmci.com!in1.uu.net!inews.intel.com!itnews.sc.intel.com!chnews!ornews.intel.com!news.jf.intel.com!haertel From: haertel@ichips.intel.com (Mike Haertel) Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system Subject: Re: The better (more suitable)Unix?? FreeBSD or Linux Date: 12 Feb 1996 18:46:22 GMT Organization: Intel Corporation Lines: 39 Message-ID: <4fo1tu$n31@news.jf.intel.com> References: <4er9hp$5ng@orb.direct.ca> <4fg8fe$j9i@pell.pell.chi.il.us> <311C5EB4.2F1CF0FB@freebsd.org> <4fjodg$o8k@venger.snds.com> NNTP-Posting-Host: pdx007.intel.com Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:14163 comp.os.linux.development.system:17781 In article <4fjodg$o8k@venger.snds.com>, Michael Griffith <grif@hill.ucr.edu> wrote: > Writing metadata synchronously and data asynchronously > can put a filesystem in a state that has undetectable > errors. For some reason, in this sync-vs-async metadata discussion, someone always brings up the claim that synchronous metadata updates can leave you in a situation where fsck reports no errors, yet you can have bogus data. True. Then they claim that async metadata update is superior, because it doesn't have this problem. FALSE! It could perfectly well happen that your async metadata update might purely by chance choose a block ordering which would leave the file system structure consistent, yet leave data blocks out of date. So this claim is bogus. As far as I know, the only practical difference between sync and async metadata update is that async results in faster write performance, especially for small files. There may be reliability differences, but I have yet to see any adequate empirical results to convince me. My gut feeling is that async requires a more sophisticated fsck, and that even so the resulting fsck may be more easily confused. However, this is just a gut feeling. It would be really neat if someone would do the reliability study that Jordon suggested... -- Mike Haertel <haertel@ichips.intel.com> Not speaking for Intel.