Date: Mon, 08 Mar 2010 20:39:15 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: Scot Hetzel <swhetzel@gmail.com> Cc: xcllnt@mac.com, Pete French <petefrench@ticketswitch.com>, freebsd-geom@freebsd.org Subject: Re: another gpt vs mbr (sanity) check Message-ID: <4B954453.1020404@icyb.net.ua> In-Reply-To: <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com> References: <761C8533-B1DC-4DC7-8B2E-9CB1A8A5BEF8@mac.com> <E1Noh4B-000JjD-5u@dilbert.ticketswitch.com> <790a9fff1003081016q2b6a7d93qa55055aaaa9cf74@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
on 08/03/2010 20:16 Scot Hetzel said the following: > On Mon, Mar 8, 2010 at 11:48 AM, Pete French > <petefrench@ticketswitch.com> 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4B954453.1020404>