From owner-freebsd-current@FreeBSD.ORG Wed Sep 21 13:53:07 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6FC4C106566C for ; Wed, 21 Sep 2011 13:53:07 +0000 (UTC) (envelope-from wblock@wonkity.com) Received: from wonkity.com (wonkity.com [67.158.26.137]) by mx1.freebsd.org (Postfix) with ESMTP id 2E2348FC17 for ; Wed, 21 Sep 2011 13:53:06 +0000 (UTC) Received: from wonkity.com (localhost [127.0.0.1]) by wonkity.com (8.14.5/8.14.5) with ESMTP id p8LDr5Uk006069; Wed, 21 Sep 2011 07:53:05 -0600 (MDT) (envelope-from wblock@wonkity.com) Received: from localhost (wblock@localhost) by wonkity.com (8.14.5/8.14.5/Submit) with ESMTP id p8LDr56H006066; Wed, 21 Sep 2011 07:53:05 -0600 (MDT) (envelope-from wblock@wonkity.com) Date: Wed, 21 Sep 2011 07:53:05 -0600 (MDT) From: Warren Block To: Thomas Mueller In-Reply-To: <20110921082649.9616D1065672@hub.freebsd.org> Message-ID: References: <20110920210906.GG14862@over-yonder.net> <20110921082649.9616D1065672@hub.freebsd.org> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (wonkity.com [127.0.0.1]); Wed, 21 Sep 2011 07:53:05 -0600 (MDT) Cc: freebsd-current@freebsd.org Subject: Re: 9.0 beta2 & the new bsdinstaller X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Sep 2011 13:53:07 -0000 On Wed, 21 Sep 2011, Thomas Mueller wrote: >>> From "Matthew D. Fuller" : > >> I've been meaning to mention this, but we really should document >> somewhere that it has a _MAXIMUM_ size. > >> I setup a system a few weeks back with GPT, and figured I'd just make >> the first 'real' partition start at the 1 meg mark. And make >> everything before that (1 meg - the however many sectors for the pmbr) >> the freebsd-boot partition. > >> It worked fine, up 'till the point that I tried to boot, and it >> completely failed to, complaining that the boot code was too big. I >> had to track around in pmbr to find > >> . . cmp $0x9000,%ax.. . # Don't load past 0x90000, >> . . jae err_big.. . # 545k should be enough for >> . . mov %ax,%es.. . # any boot code. :) > >> and redo the partition to 512k (leaving a few hundred k unused before >> the next partition started) before it would boot. That's a little >> nerve-wracking to hit on a critical system... > > I don't think there is any particular advantage in aligning GPT partitions on 1 MB boundaries. Agreed. But Windows 7 also starts the main partition at 1M. Taking that as a standard could provide compatibility with other (admittedly poorly-written) disk partitioning software. And it might not, but if it helps with POLA for people used to using GPT elsewhere, that's not a bad reason either. The bug shown above means the freebsd-boot partition should be limited to 512K at present. Another 512K of space after that doesn't really cost anything. If that extra space is needed later, it can be used without repartitioning.