Date: Mon, 17 Nov 2014 00:28:03 -0800 From: perryh@pluto.rain.com (Perry Hutchison) To: lists@natserv.net Cc: mwlucas@michaelwlucas.com, freebsd-geom@freebsd.org Subject: Re: Gmirror vs 10 Release-P12 Message-ID: <5469b193.lkIZWruTiJ873IFy%perryh@pluto.rain.com> In-Reply-To: <5468F9D6.4020300@natserv.net> References: <5465580A.6070609@natserv.net> <20141114161658.GA1719@mail.michaelwlucas.com> <5468F9D6.4020300@natserv.net>
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Francisco Reyes <lists@natserv.net> wrote: > On 11/14/2014 11:16 AM, Michael W. Lucas wrote: > > I believe 9+ GPT partitioning doesn't work with gmirror on a whole > > disk. Pardon the narcissistic link, but: > > But it was a 10.0 Release > To recap.. > 10.0 Release.. gmirror works. That was either a bug in 10.0 Release, or an accident. > Updated to 10-P12... gmirror no longer worked. As expected. > For now went without gmirror altogether. The client needed the machine > ASAP. May try upgrading to 10.1 later afer it has been out longer. 10.1 should make no difference. The problem is that, per the GPT spec, the GPT partition data appears in both the first and last blocks of the physical drive. That conflicts with applying gmirror to the entire drive, since gmirror uses the last block of whatever provider it is hosted on. If you try to gmirror the whole drive, and GPT-partition the mirror, a strict BIOS will complain about the absence of the GPT data in the drive's last physical block and/or about the size in the GPT not matching the size reported by the drive. The proper way to use gmirror on a GPT disk is to mirror individual partitions, rather than the whole drive. Yes, this can be a nuisance -- if you have 5 partitions you need 5 mirrors rather than just one. Another approach is to make just one GPT partition, gmirror that, and then MBR-partition that mirror. However getting this scheme to work on the boot drive requires hacking the boot blocks.
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