From owner-freebsd-arch@FreeBSD.ORG Sun Jan 3 06:36:55 2010 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 596C8106566C; Sun, 3 Jan 2010 06:36:55 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from pooker.samsco.org (pooker.samsco.org [168.103.85.57]) by mx1.freebsd.org (Postfix) with ESMTP id C36818FC14; Sun, 3 Jan 2010 06:36:54 +0000 (UTC) Received: from [IPv6:::1] (pooker.samsco.org [168.103.85.57]) (authenticated bits=0) by pooker.samsco.org (8.14.2/8.14.2) with ESMTP id o036aUmA071289; Sat, 2 Jan 2010 23:36:30 -0700 (MST) (envelope-from scottl@samsco.org) Mime-Version: 1.0 (Apple Message framework v1076) Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes From: Scott Long In-Reply-To: <71177.1262471841@critter.freebsd.dk> Date: Sat, 2 Jan 2010 23:36:30 -0700 Content-Transfer-Encoding: 7bit Message-Id: References: <71177.1262471841@critter.freebsd.dk> To: Poul-Henning Kamp X-Mailer: Apple Mail (2.1076) X-Spam-Status: No, score=-4.2 required=3.8 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.8 X-Spam-Checker-Version: SpamAssassin 3.1.8 (2007-02-13) on pooker.samsco.org Cc: =?iso-8859-1?Q?Ulrich_Sp=F6rlein?= , Miroslav Lachman <000.fbsd@quip.cz>, Thomas Backman , freebsd-current@freebsd.org, Julian Elischer , freebsd-arch@freebsd.org, Pieter de Goeje , Alexander Motin Subject: Re: File system blocks alignment X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 03 Jan 2010 06:36:55 -0000 On Jan 2, 2010, at 3:37 PM, Poul-Henning Kamp wrote: > In message <4B3FC8A2.1090901@elischer.org>, Julian Elischer writes: >> Poul-Henning Kamp wrote: >>> You overlook that MBR/Fdisk requires bootable slices to start at a >>> "track". That means that the propper slice-alignmen typically >>> will be 8*63=504 sectors. >> >> No it doesn't, (or at least it didn't) but it has become custom to >> do so. > > Yes it does, for all slices not starting on the first head. > > We've been over this maddness in the past multiple times. Julian is correct, LBA and packet mode has left the CHS madness as nothing more than a historical blemish. For many many years, we set up our FreeBSD systems at Yahoo to create a bootable Slice 1 at sector 512, and it worked just fine. Given that we use a multitude of vendors and BIOSes, our sample size is fairly significant. IIRC, BIOS vendors switched to packet mode around 2001-2002, and maybe as late as 2003 for some late adopters, but certainly no later than that. That was 8-9 years ago, roughly half of FreeBSD's present age. I don't know for sure, but I'd bet that packet mode has been a WHQL item since at least WinXP, and thus pretty much guaranteed to be present in the vast majority of operational hardware out there. Despite all of this, I do recognize and appreciate your concern for compatibility. That's why I really like John Baldwin's hybrid MBR+GPT solution, as it appears to bridge compatibility while breaking away from the CHS and MBR constraints. We switched to it at Yahoo several years ago, and it also works very well for us. Scott