Date: Tue, 3 Dec 2013 13:35:00 -0700 (MST) From: Warren Block <wblock@wonkity.com> To: Julien Cigar <jcigar@ulb.ac.be> Cc: "Mike." <the.lists@mgm51.com>, freebsd-questions@freebsd.org Subject: Re: gmirror, gpart and MBR vs GPT in the Handbook Message-ID: <alpine.BSF.2.00.1312031334390.24898@wonkity.com> In-Reply-To: <20131203173700.GD86280@mordor.lan> References: <201311301303210813.05DE187E@smtp.24cl.home> <alpine.BSF.2.00.1311301352140.99113@wonkity.com> <201312011121580096.005D00FB@smtp.24cl.home> <20131202103122.GN66981@mordor.lan> <alpine.BSF.2.00.1312020847510.14007@wonkity.com> <20131203092604.GA86280@mordor.lan> <alpine.BSF.2.00.1312030920040.23862@wonkity.com> <20131203173700.GD86280@mordor.lan>
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On Tue, 3 Dec 2013, Julien Cigar wrote: > On Tue, Dec 03, 2013 at 09:27:12AM -0700, Warren Block wrote: >> On Tue, 3 Dec 2013, Julien Cigar wrote: >> >>> On Mon, Dec 02, 2013 at 08:56:13AM -0700, Warren Block wrote: >>>> On Mon, 2 Dec 2013, Julien Cigar wrote: >>>> >>>>> If you want to use GPT with gmirror you may want to mirror each >>>>> partition instead of the whole disk. >>>>> >>>>> For example on my box I have the following: https://dpaste.de/Rb3S >>>> >>>> There are a couple of potential problems with that. The big one is when >>>> a disk fails and is replaced. If you're not careful, the rebuild of all >>>> those mirrored partitions will start at the same time. Head contention >>>> will bring that to a near-standstill. It also puts a heavy load on the >>>> drive that still works. Hopefully it is not the same model and age as >>>> the one that failed, or its "warranty timer" may also be close to >>>> expiring. >>> >>> That's true, I turned off autosynchronization of stale components to >>> avoid this kind of bad scenario .. >>> >>>> >>>> A less-serious problem is that only the partitions are mirrored. That >>>> leaves out metadata like the partition tables and bootcode, but those >>>> typically do not change very often and might not be a problem. The >>>> admin has to remember to manually install such things on a new >>>> replacement disk, though. >>> >>> It's just a matter of gpart backup / gpart restore, right ? >> >> That will get the partition tables but not the bootcode or PMBR. A >> failed disk could then leave a mirror which has all the data but is >> unbootable. > > ok, so I've to be sure that: > > $> gpart bootcode -b /boot/pmbr -p gptboot -i 1 adaX > > is executed for each disk involved in the mirror, right ..? That's correct.
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