From owner-freebsd-doc@FreeBSD.ORG Thu May 17 22:27:05 2012 Return-Path: Delivered-To: doc@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 776CD106566B for ; Thu, 17 May 2012 22:27:05 +0000 (UTC) (envelope-from mexas@bristol.ac.uk) Received: from dirg.bris.ac.uk (dirg.bris.ac.uk [137.222.10.102]) by mx1.freebsd.org (Postfix) with ESMTP id 2DE608FC08 for ; Thu, 17 May 2012 22:27:05 +0000 (UTC) Received: from ncsd.bris.ac.uk ([137.222.10.59] helo=ncs.bris.ac.uk) by dirg.bris.ac.uk with esmtp (Exim 4.72) (envelope-from ) id 1SV99u-0002iq-HK; Thu, 17 May 2012 23:26:58 +0100 Received: from mech-cluster241.men.bris.ac.uk ([137.222.187.241]) by ncs.bris.ac.uk with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1SV99u-0004iz-2d; Thu, 17 May 2012 23:26:58 +0100 Received: from mech-cluster241.men.bris.ac.uk (localhost [127.0.0.1]) by mech-cluster241.men.bris.ac.uk (8.14.5/8.14.5) with ESMTP id q4HMQvaN014422; Thu, 17 May 2012 23:26:57 +0100 (BST) (envelope-from mexas@bris.ac.uk) Received: (from mexas@localhost) by mech-cluster241.men.bris.ac.uk (8.14.5/8.14.5/Submit) id q4HMQvJZ014421; Thu, 17 May 2012 23:26:57 +0100 (BST) (envelope-from mexas@bris.ac.uk) X-Authentication-Warning: mech-cluster241.men.bris.ac.uk: mexas set sender to mexas@bris.ac.uk using -f Date: Thu, 17 May 2012 23:26:57 +0100 From: Anton Shterenlikht To: Warren Block Message-ID: <20120517222657.GA14370@mech-cluster241.men.bris.ac.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i Cc: doc@freebsd.org Subject: Re: Handbook mirroring section X-BeenThere: freebsd-doc@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Documentation project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 17 May 2012 22:27:05 -0000 On Thu, May 17, 2012 at 03:17:29PM -0600, Warren Block wrote: > Summary: Handbook mirror example broken, new rewrite here, feedback > desired before commit. > > http://www.wonkity.com/~wblock/mirror/book.html > http://www.wonkity.com/~wblock/mirror/chapter.diff > > > More detail: > > The existing mirroring section in the GEOM chapter of the Handbook uses > a workaround to add another drive and make a mirror with one existing > drive without moving data. > > http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html > > That workaround creates mirrors that FreeBSD 9 and later versions of 8 > see as having invalid, overlapping areas. The more strict tests prevent > at least FreeBSD 9 from even booting from mirrors created that way: > > http://www.freebsd.org/releases/9.0R/relnotes-detailed.html#AEN1277 > > Ideally, the procedure would be able to create a single-drive mirror but > use only a limited amount of disk space on the new drive, making that > space the same size as the existing drive. (Here's a new 80G drive, but > I only want to use 40G of space for the mirror.) Of course this can be > done with partitions, but that is more complex and there may be > thrashing issues with multiple partitions. > > It turns out to be fairly difficult to do this in a situation that will > work reliably for the average user. > > I've rewritten the mirroring section to just use two new drives. > > A mirror *can* be created with two different-sized drives, provided they > are both seen at the time of creation. The smaller size is used; > exposing that size with a command-line option would be very useful. I haven't read your update thoroughly. This is just to mention that you might want to look at http://www.freebsd.org/cgi/query-pr.cgi?pr=docs/136712 It might be completely out of date by now, in which case feel free to close this PR. -- Anton Shterenlikht Room 2.6, Queen's Building Mech Eng Dept Bristol University University Walk, Bristol BS8 1TR, UK Tel: +44 (0)117 331 5944 Fax: +44 (0)117 929 4423