From owner-freebsd-questions@FreeBSD.ORG Thu Jun 12 07:25:37 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 57BD81065671 for ; Thu, 12 Jun 2008 07:25:37 +0000 (UTC) (envelope-from iwrTech@iwr.ru.ac.za) Received: from c.mail.ru.ac.za (c.mail.ru.ac.za [IPv6:2001:4200:1010::25:3]) by mx1.freebsd.org (Postfix) with ESMTP id 7E8248FC13 for ; Thu, 12 Jun 2008 07:25:36 +0000 (UTC) (envelope-from iwrTech@iwr.ru.ac.za) Received: from iwr.ru.ac.za ([146.231.64.249]:54637) by c.mail.ru.ac.za with esmtp (Exim 4.68 (FreeBSD)) (envelope-from ) id 1K6hBe-000CFY-ON for freebsd-questions@freebsd.org; Thu, 12 Jun 2008 09:25:34 +0200 Received: from iwr61.iwr.ru.ac.za ([146.231.64.161]) by iwr.ru.ac.za with esmtp (Exim 4.69 (FreeBSD)) (envelope-from ) id 1K6hBe-0000Aj-OC for freebsd-questions@freebsd.org; Thu, 12 Jun 2008 09:25:34 +0200 From: "DA Forsyth" Organization: IWR To: freebsd-questions@freebsd.org Date: Thu, 12 Jun 2008 09:25:31 +0200 MIME-Version: 1.0 Message-ID: <4850EB8B.12487.4CC2C0F4@iwrtech.iwr.ru.ac.za> Priority: normal In-reply-to: <20080610145926.GA66984@owl.midgard.homeip.net> References: <484EACEB.7169.43FE1258@iwrtech.iwr.ru.ac.za>, <20080610145926.GA66984@owl.midgard.homeip.net> X-mailer: Pegasus Mail for Windows (4.41) Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Content-description: Mail message body X-Virus-Scanned: c.mail.ru.ac.za (146.231.129.35) Subject: Re: xRAID disks.... X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: iwrTech@iwr.ru.ac.za List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 12 Jun 2008 07:25:37 -0000 On 10 Jun 2008 , Erik Trulsson entreated about "Re: xRAID disks....": > > I suspect the raidinfo is stored on the disk somewhere and a suitable > > 'dd' command can erase it. but where and how? > > That kind of information is usually stored last on the disk (where it is > least likely to be overwritten by filesystems, partitioning info, or boot > loaders), so if you overwrite the last couple of KBs on those disks you will > probably be fine. > (If you want to be certain you can always use 'dd' to nuke all the > information on the disk. That will take longer time, but you get the extra > advantage of testing all the blocks on the disk so that they work > correctly.) > > For the first you could do something like: > dd if=/dev/zero of=/dev/ad1 bs=1m skip=76318 > which should overwrite the last MB of ad1 with zeros. I tried to overwrite just the last sector, but though dd reported success (and took ages, seems it has to do a read for every skipped sector) the data was still there when I used dd to display it. I have just done a search for sector editing software but I cannot find anything in ports. Starting to think of writing some C... how hard can it be just to seek to a given sector and scribble zeros on it? so then I did this (overwrite last megabyte)and that did in fact zero the last megabyte, taking away the raid info AND all the partition info. not exactly what I wanted but I was going to repartition anyway. but I now have another disk with data and raid info on it and will need a way to nondestructively remove the raid info there. I did try the suggestion of 'atacontrol' but it did nothing, I also tried 'gmirror clear' but that gives an error message, maybe I should first create a gmirror then clear it. or maybe try the 'forget' command.... hmmm, thinking now the gmirror create/remove route will probably work. let me try it on a blankish disk and see.... -- DA Fo rsyth Network Supervisor Principal Technical Officer -- Institute for Water Research http://www.ru.ac.za/institutes/iwr/