Date: Thu, 23 Aug 2007 10:55:32 -0500 From: CyberLeo Kitsana <cyberleo@cyberleo.net> To: Ian Smith <smithi@nimnet.asn.au> Cc: Chris <chrcoluk@gmail.com>, freebsd-questions@freebsd.org, Bill Moran <wmoran@potentialtech.com> Subject: Re: fsck strangeness Message-ID: <46CDADF4.5070801@cyberleo.net> In-Reply-To: <Pine.BSF.3.96.1070823144008.26941B-100000@gaia.nimnet.asn.au> References: <Pine.BSF.3.96.1070823144008.26941B-100000@gaia.nimnet.asn.au>
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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. -- Fuzzy love, -CyberLeo Technical Administrator CyberLeo.Net Webhosting http://www.CyberLeo.Net <CyberLeo@CyberLeo.Net> Furry Peace! - http://wwww.fur.com/peace/
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