From owner-freebsd-questions@FreeBSD.ORG Thu Aug 23 15:55:41 2007 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1BF7E16A419 for ; Thu, 23 Aug 2007 15:55:41 +0000 (UTC) (envelope-from cyberleo@cyberleo.net) Received: from pizzabox.cyberleo.net (alpha.cyberleo.net [198.145.45.10]) by mx1.freebsd.org (Postfix) with ESMTP id B68BB13C461 for ; Thu, 23 Aug 2007 15:55:40 +0000 (UTC) (envelope-from cyberleo@cyberleo.net) Received: (qmail 70967 invoked from network); 23 Aug 2007 15:55:40 -0000 Received: from adsl-75-3-84-39.dsl.chcgil.sbcglobal.net (HELO ?172.16.44.14?) (cyberleo@cyberleo.net@75.3.84.39) by alpha.cyberleo.net with ESMTPA; 23 Aug 2007 15:55:40 -0000 Message-ID: <46CDADF4.5070801@cyberleo.net> Date: Thu, 23 Aug 2007 10:55:32 -0500 From: CyberLeo Kitsana User-Agent: Thunderbird 2.0.0.6 (X11/20070819) MIME-Version: 1.0 To: Ian Smith References: In-Reply-To: Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Chris , freebsd-questions@freebsd.org, Bill Moran Subject: Re: fsck strangeness X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Aug 2007 15:55:41 -0000 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 Furry Peace! - http://wwww.fur.com/peace/