From owner-freebsd-hackers@FreeBSD.ORG Fri Jul 28 22:36:31 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 ABC2716A4DF; Fri, 28 Jul 2006 22:36:31 +0000 (UTC) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by mx1.FreeBSD.org (Postfix) with ESMTP id 73DD043D49; Fri, 28 Jul 2006 22:36:29 +0000 (GMT) (envelope-from dillon@apollo.backplane.com) Received: from apollo.backplane.com (localhost [127.0.0.1]) by apollo.backplane.com (8.13.4.20060308/8.13.4) with ESMTP id k6SMaRsT089447; Fri, 28 Jul 2006 15:36:27 -0700 (PDT) Received: (from dillon@localhost) by apollo.backplane.com (8.13.4.20060308/8.13.4/Submit) id k6SMaRlj089446; Fri, 28 Jul 2006 15:36:27 -0700 (PDT) Date: Fri, 28 Jul 2006 15:36:27 -0700 (PDT) From: Matthew Dillon Message-Id: <200607282236.k6SMaRlj089446@apollo.backplane.com> To: Andreas Klemm References: <20060727063936.GA1246@titan.klemm.apsfilter.org> <20060727122159.GB4217@britannica.bec.de> <20060727202528.GA14954@titan.klemm.apsfilter.org> Cc: freebsd-hackers@freebsd.org Subject: Re: disklabel differences FreeBSD, DragonFly 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: Fri, 28 Jul 2006 22:36:31 -0000 :On Thu, Jul 27, 2006 at 02:21:59PM +0200, Joerg Sonnenberger wrote: :> On Thu, Jul 27, 2006 at 08:39:37AM +0200, Andreas Klemm wrote: :> > Later I wanted to mount the dfly filesystems on FreeBSD 6.1, :> > of course still my main Unix ;-) But it wasn't possible. :> :> DragonFly disklabels allow 16 entries by default, FreeBSD still limits :> it to 8. That's why you can't read it directly. :> : :Hmm, for the sake of compatibility, wouldn't it have been an option, :to add this extra bit to the end of the struct ? : : Andreas /// : :-- :Andreas Klemm - Powered by FreeBSD 6 The thing to note here is that FreeBSD had to make room for the UFS1+UFS2 boot code, so it moved the boot code back to the point where it abuts the 8-partition-sized disklabel. So at least insofar as FreeBSD goes, the partition table cannot be expanded to 16 partitions with UFS1+UFS2 boot code. I'm guessing that it *could* be expanded to 16 partitions with UFS1 only or UFS2 only boot code (assuming the boot code were relocated back to where it was originally in FreeBSD-4/5 times, before UFS2 came along). With regards to simply recognizing a DragonFly partition... yes, that would be easy to do. Since FreeBSD is now devfs-based, the bit we had to steal to support 16 partitions in /dev isn't an issue. I dunno if geom changes the equation any. Personally I have always felt that 8 partitions is restrictive. My main home server has 10 and the main DragonFly box has 11. There is another solution for FreeBSD folks, however. You *DO* have four slices to play with. You can put a disklabel with 8 partitions in it on each one (for 32 total). It isn't as convenient, but it does work. -Matt Matthew Dillon