From owner-freebsd-geom@FreeBSD.ORG Fri Sep 16 07:30:18 2005 Return-Path: X-Original-To: freebsd-geom@freebsd.org Delivered-To: freebsd-geom@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4585716A41F for ; Fri, 16 Sep 2005 07:30:18 +0000 (GMT) (envelope-from sudakov@sibptus.tomsk.ru) Received: from relay2.tomsk.ru (relay2.tomsk.ru [212.73.124.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7E06043D46 for ; Fri, 16 Sep 2005 07:30:17 +0000 (GMT) (envelope-from sudakov@sibptus.tomsk.ru) X-Virus-Scanned: by Dr.Web (R) daemon for FreeBSD, version 4.32.1 (2004-08-30) at relay2.tomsk.ru X-Spam-Checker-Version: SpamAssassin 3.0.4 on relay2.tomsk.ru Received: from [172.16.138.125] (account sudakovva@sibptus.tomsk.ru HELO admin.sibptus.tomsk.ru) by relay2.tomsk.ru (CommuniGate Pro SMTP 4.3.2) with ESMTPSA id 1201837 for freebsd-geom@freebsd.org; Fri, 16 Sep 2005 14:30:13 +0700 Received: (from sudakov@localhost) by admin.sibptus.tomsk.ru (8.12.9p2/8.12.9/Submit) id j8G7UCcI031229 for freebsd-geom@freebsd.org; Fri, 16 Sep 2005 14:30:12 +0700 (OMSST) (envelope-from sudakov) Date: Fri, 16 Sep 2005 14:30:12 +0700 From: Victor Sudakov To: freebsd-geom@freebsd.org Message-ID: <20050916073012.GA31056@admin.sibptus.tomsk.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.1i Organization: AO "Svyaztransneft", SibPTUS X-PGP-Key: http://vas.tomsk.ru/vas.asc Subject: Create a mirror on disk with valid data X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Sep 2005 07:30:18 -0000 Colleagues, gmirror(8) says that a mirror can be created from a disk with existing data. However, other sources like http://ezine.daemonnews.org/200502/diskmirror.html say that the mirror device should be first partitioned, labelled and formatted. The second way seems to me more feasible. From experimenting with different disks I have found out that (according to fdisk) the size of gm0 is several sectors smaller than that of ad0. I said to myself, that is the overhead of the gmirror metadata. How could it then be possible to create a mirror from a disk with existing data, like the man page suggests? The gmirror metadata could then be overwritten with user data or vice versa. Any input is very much appreciated. -- Victor Sudakov, VAS4-RIPE, VAS47-RIPN