From owner-freebsd-hackers@FreeBSD.ORG Mon Jul 31 20:50:45 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3493A16A4DD for ; Mon, 31 Jul 2006 20:50:45 +0000 (UTC) (envelope-from dan@dan.emsphone.com) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id D0C9343D46 for ; Mon, 31 Jul 2006 20:50:44 +0000 (GMT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.13.1/8.13.4) id k6VKoikt021060 for freebsd-hackers@freebsd.org; Mon, 31 Jul 2006 15:50:44 -0500 (CDT) (envelope-from dan) Date: Mon, 31 Jul 2006 15:50:44 -0500 From: Dan Nelson To: freebsd-hackers@freebsd.org Message-ID: <20060731205043.GD63872@dan.emsphone.com> References: <20060731203213.GA75233@hades.panopticon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060731203213.GA75233@hades.panopticon> X-OS: FreeBSD 5.5-PRERELEASE X-message-flag: Outlook Error User-Agent: Mutt/1.5.12-2006-07-14 Subject: Re: absolute vs. relative offsets in disklabel X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Jul 2006 20:50:45 -0000 In the last episode (Aug 01), Dmitry Marakasov said: > Recent `disklabel differences FreeBSD, DragonFly' thread gave me a > thought - why do we have absolute offsets in disklabel? AFAIK, on > NetBSD and OpenBSD, label is not necessarily located `near' > filesystems stored in it's partitions - and even disklabel utility > shows absolute offsets (with 'c' covering entire device). FreeBSD, > however, seem to step far away from that standart - 8 partitions > instead of 16, label located in the beginning of a partition, > bsdlabel shows relative offsets. Now I wonder if there are any > reasons for offsets to be actually absolute? There are many weighty > arguments for relative offsets: I asked this question a few years ago after having problems dd'ing a FreeBSD installation from one disk to another, and the answer was "it's always been that way" :) It shouldn't be too hard to have the code autodetect whether the offsets are relative or absolute by looking at what the 'c' partition's offset is. -- Dan Nelson dnelson@allantgroup.com