From owner-freebsd-geom@FreeBSD.ORG Mon Mar 8 18:39:22 2010 Return-Path: Delivered-To: freebsd-geom@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C1C0A1065676 for ; Mon, 8 Mar 2010 18:39:22 +0000 (UTC) (envelope-from avg@icyb.net.ua) Received: from citadel.icyb.net.ua (citadel.icyb.net.ua [212.40.38.140]) by mx1.freebsd.org (Postfix) with ESMTP id 0AFC18FC1A for ; Mon, 8 Mar 2010 18:39:21 +0000 (UTC) Received: from porto.topspin.kiev.ua (porto-e.starpoint.kiev.ua [212.40.38.100]) by citadel.icyb.net.ua (8.8.8p3/ICyb-2.3exp) with ESMTP id UAA09314; Mon, 08 Mar 2010 20:39:16 +0200 (EET) (envelope-from avg@icyb.net.ua) Received: from localhost.topspin.kiev.ua ([127.0.0.1]) by porto.topspin.kiev.ua with esmtp (Exim 4.34 (FreeBSD)) id 1NohrH-0000e3-Ul; Mon, 08 Mar 2010 20:39:16 +0200 Message-ID: <4B954453.1020404@icyb.net.ua> Date: Mon, 08 Mar 2010 20:39:15 +0200 From: Andriy Gapon User-Agent: Thunderbird 2.0.0.23 (X11/20100211) MIME-Version: 1.0 To: Scot Hetzel References: <761C8533-B1DC-4DC7-8B2E-9CB1A8A5BEF8@mac.com> <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com> In-Reply-To: <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com> X-Enigmail-Version: 0.96.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: xcllnt@mac.com, Pete French , freebsd-geom@freebsd.org Subject: Re: another gpt vs mbr (sanity) check X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Mar 2010 18:39:22 -0000 on 08/03/2010 20:16 Scot Hetzel said the following: > On Mon, Mar 8, 2010 at 11:48 AM, Pete French > wrote: >>> To clarify: the protective MBR is there only to protect the GPT >>> disk from tools that do not understand the GPT. Any GPT-aware >>> tool will treat the disk as a GPT disk. Consequently: the MBR >>> is inferior to the GPT... >> The queston is then, why isn't Windows treating it as GPT ? It's > > I have both MBR and GPT formated drives installed in my laptop, and > Windows 7 correctly identifies both drives. The GPT drive was > formated using FreeBSD 8. > >> all very nice in theory, but if the practical upshot is that >> we get flash media which will read perfectly well in all operating >> systems except for BSD then thats not a good result, even if it >> is theoretically correct. Which is the situation the original poster >> appeared to have. >> > > The problem the original poster was having is this: > > Format drive as GPT > Re-Format drive as MBR > > FreeBSD still sees the drive as GPT instead of MBR. > > The reason is that FreeBSD is still detecting the Seconday GPT which > is located at the end of the disk, and using it due to the Primary GPT > was lost/corrupted when the drive was reformated as MBR disk. Not exactly true - primary GPT (in sector 1) was also intact. Typical MBR formatting reserves sectors 1-62, but doesn't actually put anything there. > The real question is how was the drive reformated. If it was > reformated using gpart: > > - Delete all existing partitions: > gpart delete -i X adY > - Destroy the GPT formated drive > gpart destroy adY > - Create the MBR formated drive > gpart create -s mbr adY > > And the secondary GPT header still exists, then it is a FreeBSD bug. > But if it was reformated using a different tool, then it is a bug in > that tool for not reconizing that the original disk was formated as > GPT. It was formatted either with GPT-unaware tool, which is not a deadly sin (or a bug), or with a tool that simply ignored anything already on the disk by design. -- Andriy Gapon