Date: Fri, 25 Jul 2014 07:45:23 -0600 (MDT) From: Warren Block <wblock@wonkity.com> To: "Patrick M. Hausen" <hausen@punkt.de> Cc: freebsd-stable@freebsd.org Subject: Re: Gmirror + gpart corruption on 9.3-PRE Message-ID: <alpine.BSF.2.11.1407250732360.67669@wonkity.com> In-Reply-To: <E15BCB9E-F569-47E6-A63E-59B9AD2E5D3F@punkt.de> References: <53D1BDB2.7030906@jetcafe.org> <alpine.BSF.2.11.1407242120070.3624@wonkity.com> <53D1DD47.4040403@jetcafe.org> <alpine.BSF.2.11.1407242310280.41111@wonkity.com> <E15BCB9E-F569-47E6-A63E-59B9AD2E5D3F@punkt.de>
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On Fri, 25 Jul 2014, Patrick M. Hausen wrote: > Am 25.07.2014 um 07:34 schrieb Warren Block <wblock@wonkity.com>: >> True. But partitioning can be specific to the drive. It's not like GPT-partitioned drives can be copied with dd (well, not correctly). > > Errrr ... sorry, but ... could you please elaborate on that? Up until now I was sure that any drive could be > copied with dd(1). > > Puzzled. :-) GPT partitioning puts a primary partition table at the beginning of the drive, and a backup partition table at the end of the drive. Use dd to copy a 500G drive to a 1TB drive, and that backup partition is now in the middle of the drive. If the drives are even a single block different in size, that backup table will be in the wrong place, not found by the software and effectively lost. This is dd's bug/feature: it does not understand the data being copied. gpart(8) can back up and restore partition tables between differently-sized drives, and does it correctly.
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