From owner-freebsd-current@FreeBSD.ORG Thu Oct 6 14:16:12 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 C44611065670 for ; Thu, 6 Oct 2011 14:16:12 +0000 (UTC) (envelope-from daniel@digsys.bg) Received: from smtp-sofia.digsys.bg (smtp-sofia.digsys.bg [193.68.3.230]) by mx1.freebsd.org (Postfix) with ESMTP id 4CF6B8FC16 for ; Thu, 6 Oct 2011 14:16:11 +0000 (UTC) Received: from dcave.digsys.bg (dcave.digsys.bg [192.92.129.5]) (authenticated bits=0) by smtp-sofia.digsys.bg (8.14.4/8.14.4) with ESMTP id p96EFrUl052717 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Thu, 6 Oct 2011 17:15:59 +0300 (EEST) (envelope-from daniel@digsys.bg) Message-ID: <4E8DB424.6050106@digsys.bg> Date: Thu, 06 Oct 2011 16:59:00 +0300 From: Daniel Kalchev User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:6.0.2) Gecko/20110917 Thunderbird/6.0.2 MIME-Version: 1.0 To: Pieter de Goeje References: <1927112464.20111004220507@serebryakov.spb.ru> <4E8DA257.9080406@digsys.bg> <201110061604.15036.pieter@degoeje.nl> In-Reply-To: <201110061604.15036.pieter@degoeje.nl> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: freebsd-current@freebsd.org Subject: Re: RFC: Project geom-events 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: Thu, 06 Oct 2011 14:16:12 -0000 On 06.10.11 17:04, Pieter de Goeje wrote: > The layering *is* correct and you *can* create a GPT inside a glabel > label, but then > > 1) you get device names like /dev/label/somethingp1, > /dev/label/somethingp2, etc. >> .. and, you overwrite the last sector of the device, not of the >> provider. This is incorrect layering -- GPT should see only the provider >> it was given and nothing at different layers. > If you stack GPT on top of glabel, then your statement is not true. GPT will > overwrite the last sector of the (glabel) provider, not the underlying device. > There is no layering violation. I stand corrected. Sorry for creating confusion with this statement. Most of the time I was blaming GPT, I was actually blaming GLABEL (see below) > Because physically the first sector of the device is still GPT data the BIOS > will still try to boot from it, hence it would probably be wise to disallow > GPT on anything other then raw devices. Yes, but.. what is a raw device? Probably disallow GPT on devices that are not bootable, but how this can be indicated? GPT is very useful for it's ability to create labeled partitions. > This problem wouldn't exist if geom classes would write their metadata to the > first sector, but then you could no longer boot from for example > gmirrored/glabeled devices with a MBR. > We seem to blame GPT here, but it is really GLABEL the culprit here. If GLABEL writes to the first sector of the provider and that makes the disk non-bootable, then there is little chance that somebody will try to use first GLABEL, then GPT etc and create the current situation. Unfortunately, the GLABEL + GMIRROR setup is so common..