From owner-freebsd-questions@FreeBSD.ORG Tue Dec 3 20:35:03 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 17546181 for ; Tue, 3 Dec 2013 20:35:03 +0000 (UTC) Received: from wonkity.com (wonkity.com [67.158.26.137]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id A41CE108E for ; Tue, 3 Dec 2013 20:35:02 +0000 (UTC) Received: from wonkity.com (localhost [127.0.0.1]) by wonkity.com (8.14.7/8.14.7) with ESMTP id rB3KZ1rE025933; Tue, 3 Dec 2013 13:35:01 -0700 (MST) (envelope-from wblock@wonkity.com) Received: from localhost (wblock@localhost) by wonkity.com (8.14.7/8.14.7/Submit) with ESMTP id rB3KZ0QG025930; Tue, 3 Dec 2013 13:35:01 -0700 (MST) (envelope-from wblock@wonkity.com) Date: Tue, 3 Dec 2013 13:35:00 -0700 (MST) From: Warren Block To: Julien Cigar Subject: Re: gmirror, gpart and MBR vs GPT in the Handbook In-Reply-To: <20131203173700.GD86280@mordor.lan> Message-ID: References: <201311301303210813.05DE187E@smtp.24cl.home> <201312011121580096.005D00FB@smtp.24cl.home> <20131202103122.GN66981@mordor.lan> <20131203092604.GA86280@mordor.lan> <20131203173700.GD86280@mordor.lan> User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.4.3 (wonkity.com [127.0.0.1]); Tue, 03 Dec 2013 13:35:01 -0700 (MST) Cc: "Mike." , freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 Dec 2013 20:35:03 -0000 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.