Date: Thu, 28 Apr 2011 18:24:18 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-stable@freebsd.org Subject: Re: correct way to setup gmirror on 7.4? Message-ID: <ipc4bi$e0c$1@dough.gmane.org> In-Reply-To: <BANLkTimPQqE0cjiV2Y8vbjS87NmRiD4Zuw@mail.gmail.com> References: <BANLkTimCFcw_Oyp9RmBhfCZ9-QORUQEwfA@mail.gmail.com> <xn0hddht75xo97q00a@news.gmane.org> <20110427221554.GB22139@lava.net> <BANLkTikDjPLijvWrpK4y48fp5q6c2LnpqA@mail.gmail.com> <4DB9303E.9090305@digsys.bg> <BANLkTikUn5jRSDWmvpHV9nGuLyKT5KHg6A@mail.gmail.com> <BANLkTimAxZNrT63kDOPTN%2Bq1wOoQqf3Q5g@mail.gmail.com> <BANLkTimPQqE0cjiV2Y8vbjS87NmRiD4Zuw@mail.gmail.com>
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On 28/04/2011 17:02, Edho P Arief wrote: > On Thu, Apr 28, 2011 at 9:40 PM, Freddie Cash<fjwcash@gmail.com> wrote: >> Granted, there may be reasons why it wasn't done like this in the >> beginning, but my non-GEOM programmer's eyes can't see any. > > I believe one of the reason is it would prevent conversion from > non-gmirror disk to gmirror one as explained here > > http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html Actually, storing any kind of metadata in the first sector can lead to weird and unexpected problems with some buggy disk controllers which parse the MBR for some (wrong) reasons. I personally have a disk controller which hangs on boot if the MBR contains anything but primary partitions of DOS type (even changing the partition type makes it hang), and that is not the only disk controller I've seen with this type of a bug. The second reason is that storing anything except the MBR in the first sector makes the drive non-bootable (even if the controller is ok) and it is kind of nice to be able to make a cheap soft-RAID1 from two ordinary (S)ATA drives.
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