Date: Tue, 30 Aug 2005 03:16:32 +0200 From: Matthias Buelow <mkb@incubus.de> To: Jon Dama <jd@ugcs.caltech.edu> Cc: freebsd-stable@freebsd.org, Mark Kirkwood <markir@paradise.net.nz> Subject: Re: Sysinstall automatic filesystem size generation. Message-ID: <20050830011632.GG1462@drjekyll.mkbuelow.net> In-Reply-To: <Pine.LNX.4.53.0508291750030.20467@riyal.ugcs.caltech.edu> References: <200508291836.j7TIaVEk013147@gw.catspoiler.org> <20050829185933.GB1462@drjekyll.mkbuelow.net> <431362ED.9030800@mac.com> <20050829204714.GC1462@drjekyll.mkbuelow.net> <43137AFB.9060304@mac.com> <20050829215613.GD1462@drjekyll.mkbuelow.net> <431390A0.5080007@mac.com> <20050830002051.GE1462@drjekyll.mkbuelow.net> <4313AB8D.4010807@paradise.net.nz> <Pine.LNX.4.53.0508291750030.20467@riyal.ugcs.caltech.edu>
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Jon Dama wrote: >Ironically, phk backed out the underlying support for this safety fix > from the FreeBSD kernel b.c. it wasn't integrated into the softupdates >code >whereas in reality the proper course of action would have been to hook it >in. :-/ Can it be put into softupdates at all? From what I understand (which is probably a rather sketchy idea of the matter), write barriers work because they are only used here to separate journal writes from data writes (i.e., to make sure the log is written, by flushing the cache, before any filesystem data hits the platters). I've read the softupdates paper some time ago and haven't found similar sequence points where one could insert such flushing. One would have to "flush" all the time, either continuously or in very short intervals, in order to keep the ordering, which then would amount to the same effects as if one simply disabled the cache. But probably I'm wrong here (I hope). mkb.
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