Date: Sun, 1 Feb 2009 18:31:28 +0000 From: RW <rwmaillists@googlemail.com> To: freebsd-questions@freebsd.org Subject: Re: dump(8) using snapshot + "recommended" cache Message-ID: <20090201183128.524f16db@gumby.homeunix.com> In-Reply-To: <alpine.BSF.2.00.0902010838030.1180@qemg.org> References: <alpine.BSF.2.00.0902010838030.1180@qemg.org>
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On Sun, 1 Feb 2009 08:59:02 -0400 (AST) Andrew Hamilton-Wright <andrewhw@ieee.org> wrote: > > Hi All; > > I regularly use dump(8) with snapshots to back up my server. > > While this seems to have been working perfectly well so far, > upon (re)reading the man page for dump(8), I have noticed a > somewhat scary pair of lines in the paragraph describing > the option for -C <cachesize> (emphasis with stars mine): > > [Use of this option] will greatly improve performance > at the cost of ***dump possibly not noticing changes in > the file system*** between passes. > > ***It is recommended that you always use this option when > dumping a snapshot.*** > When you dump a snapshot there are, by definition, no changes between passes. So it's saying that in that case there in no reason not to cache.
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