Date: Fri, 24 Aug 2007 03:57:16 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: CyberLeo Kitsana <cyberleo@cyberleo.net> Cc: Chris <chrcoluk@gmail.com>, freebsd-questions@freebsd.org, Bill Moran <wmoran@potentialtech.com> Subject: Re: fsck strangeness Message-ID: <Pine.BSF.3.96.1070824035038.26941I-100000@gaia.nimnet.asn.au> In-Reply-To: <46CDADF4.5070801@cyberleo.net>
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On Thu, 23 Aug 2007, CyberLeo Kitsana wrote: > Ian Smith wrote: > > My knowledge of this is thin, despite reading McKusick's paper through > > several times, but we're told that background fsck runs on a snapshot of > > the fs concerned. How any bg fsck corrections are woven back into the > > live fs later is still a mystery to me, but that's because I still have > > an only barely superficial understanding of how snapshots work .. > > Background FSCK only repairs a small subset of filesystem > incosistencies. Specifically, those inconsistencies that softupdates > allows to occur, such as data blocks allocated out of the bitmap, but > not actually assigned to any inode. Background FSCK only needs to find > these (by looking at a fully consistent and unchanging snapshot of the > filesystem) and deallocate them in the live filesystem, a simple > operation given that it's guaranteed nothing will be using a block that > is both marked used and not assigned to anything. Thanks for that nutshell, CL. Sometimes little bits help the most <&^}=
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