From owner-freebsd-hackers@freebsd.org Sun Jul 29 21:02:20 2018 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8E8EE106389F for ; Sun, 29 Jul 2018 21:02:20 +0000 (UTC) (envelope-from freebsd-rwg@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (br1.CN84in.dnsmgr.net [69.59.192.140]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id EAB5B7A0A0 for ; Sun, 29 Jul 2018 21:02:19 +0000 (UTC) (envelope-from freebsd-rwg@pdx.rh.CN85.dnsmgr.net) Received: from pdx.rh.CN85.dnsmgr.net (localhost [127.0.0.1]) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3) with ESMTP id w6TL2CQ2062740; Sun, 29 Jul 2018 14:02:12 -0700 (PDT) (envelope-from freebsd-rwg@pdx.rh.CN85.dnsmgr.net) Received: (from freebsd-rwg@localhost) by pdx.rh.CN85.dnsmgr.net (8.13.3/8.13.3/Submit) id w6TL2Cq4062739; Sun, 29 Jul 2018 14:02:12 -0700 (PDT) (envelope-from freebsd-rwg) From: "Rodney W. Grimes" Message-Id: <201807292102.w6TL2Cq4062739@pdx.rh.CN85.dnsmgr.net> Subject: Re: Request for comments, new geom part type alias: freebsd-geom In-Reply-To: To: David Cross Date: Sun, 29 Jul 2018 14:02:12 -0700 (PDT) CC: FreeBSD Hackers X-Mailer: ELM [version 2.4ME+ PL121h (25)] MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.27 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 29 Jul 2018 21:02:20 -0000 > I'd like to propose that we create a GPT partition for geom labeled > partitions (gmirror, gstripe, geli, etc.. anything that can be 'tasted' and > automatically determined.) called 'freebsd-geom'. > > There are numerous cases where you shouldn't have a raw geom on a disk (for > example, imagine a raid 10 of a filesystem with VMs on it..on a raw disk > its possible that the lead block happens to line up with a VM disk image or > anything else a BIOS may determine is bootable). > > So the question becomes which part id to use; IF its a mirror of a swap of > UFS it seems perfectly reasonable to use freebsd-swap or freebsd-ufs (if a > bit dangerous). If its a mirror or a geli then you can again be in the > situation where the boot blocks (or something else), in certain > circumstances mistakes these for raw filesystems with similarly calamitous > results. > > Given these, it seems a 'freebsd-geom' (or similar) seems entirely > appropriate; we can mark these for what they really are, and eliminate > these cases where the system misinterprets intentions based on ambiguous > data. Do you have more details on just how your going to implement a "GPT" partition for geom labeled partitions. Though I think I understand what it is you want to do, how you describe it leads to some confusion on just what you are desiring to do. I am aware of some major issues involving gmultipath (GEOM::MULTIPATH) and gpt partitioned disks (GEOM::GPT) that due to bad tasting priorities you get bogus GPT error messages during boot if you have labeled your gmultipath devices, and infact can damage a gpt disk if you apply a multipath label onto a valid gpt disk. Please describe the "ambiguous data" as well, as I am not aware of what that would be. Thanks, -- Rod Grimes rgrimes@freebsd.org