From owner-freebsd-geom@FreeBSD.ORG Mon Mar 8 18:38:14 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 036E8106564A for ; Mon, 8 Mar 2010 18:38:14 +0000 (UTC) (envelope-from swhetzel@gmail.com) Received: from mail-iw0-f199.google.com (mail-iw0-f199.google.com [209.85.223.199]) by mx1.freebsd.org (Postfix) with ESMTP id BCB258FC17 for ; Mon, 8 Mar 2010 18:38:13 +0000 (UTC) Received: by iwn37 with SMTP id 37so383584iwn.27 for ; Mon, 08 Mar 2010 10:38:13 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=UMI92idmDTWZSKdQMfD8rMRweOOxgr1FQQuAMXNUry0=; b=kBFu0/8yI1wTXVLD+P+uvWuHEh5w2GiFPbS1PAUI/24DFcILUbQWuAplvbCom5CB9b Fba2LeCpSnxHHbwrVzBwOAj/A67JgSDajMNDHpLfZjXwb3zBWA5CnpTMvQwdkoGDgqdF IXu4iZXJwATyT/G/G5tZ2tXKZA0gXla4tuiRw= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=xsbvt35H9gn0CmRDHErR0AK8we5HnupqlIZW/RWwTT4noh3owRBbc5b4UssSEdzMhD e8pK22cI1IV+UnI2lMCGkc6Ueq1z6EoEz2rFa55wKSjss84MWtYPPpcMrvmr/+yWg5WX m1HaWzhdKT8EC+QAN7I1B29b6ATKMPuET+1Gw= MIME-Version: 1.0 Received: by 10.231.159.207 with SMTP id k15mr52133ibx.75.1268073492994; Mon, 08 Mar 2010 10:38:12 -0800 (PST) In-Reply-To: <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com> References: <761C8533-B1DC-4DC7-8B2E-9CB1A8A5BEF8@mac.com> <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com> Date: Mon, 8 Mar 2010 12:38:12 -0600 Message-ID: <790a9fff1003081038o317816dl9d5a274b63528df6@mail.gmail.com> From: Scot Hetzel To: Pete French Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: xcllnt@mac.com, avg@icyb.net.ua, 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 18:38:14 -0000 On Mon, Mar 8, 2010 at 12:16 PM, Scot Hetzel wrote: > 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. =A0The 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. > > The real question is how was the drive reformated. =A0If 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. I just had a look at the code for sys/geom/part/{g_part.c, g_part_gpt.c} and it does show that we delete the secondary GPT header when destroying a GPT formated drive. > 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. > > Scot >