From owner-freebsd-current@freebsd.org Tue Sep 27 05:58:43 2016 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 41C67BEBD82 for ; Tue, 27 Sep 2016 05:58:43 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-io0-x234.google.com (mail-io0-x234.google.com [IPv6:2607:f8b0:4001:c06::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 079C8779 for ; Tue, 27 Sep 2016 05:58:43 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-io0-x234.google.com with SMTP id 92so4911715iol.2 for ; Mon, 26 Sep 2016 22:58:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=Y+LMhUWEkJELhUUpqTJMU7d1hTZfwefdatC9tdgC2Hs=; b=N2XWfGjww+c06gkg0REl3vRmjNfFdcaEqXIg5rRK6qRBdLhUMWggJh4BFgjDJa9nHn G/YBVEuvv4XWyAi7bVucxIEIS4umj3t6LsakRVqHov+Tyf45TXWYVE+tREgu3hQtyath yx5C/k+6nWxDfVAk056o6iBxf4W9JA6salZilW/+cIAm6pb9lAbi5+ePNRXheKWjmFEm CqxUD+U5EpuYbaAztO9IYslf2X3Akb/hwvFF9efDUHXbVTxp+VdQQBzXaTBPL6NYEdYp vKtcuAPjdsWYR59o7bGjBMgF6jEeFi/J2pBhfP7hJq4XUsRmiMvAYR0yMlZNSlpdJP8a +Hmw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=Y+LMhUWEkJELhUUpqTJMU7d1hTZfwefdatC9tdgC2Hs=; b=XCMSn6DjzSQhwXzDmXt31EuLhpKSBisy9jM9w1ll/mnWbdjjNWAIrHmyBggu2nl6Gx uWFs5lb1hx4boSJv5uyflx7nC13SctexrrksevoNkLWJS9AXSon3Bck+WhgACvGFAgcz 8cIiBfiaZGyzYkQlDz6KV9WzQGMHp5xq+jTamKRG4X3Ld470M90Kl3WNj2qWz/QUPI7f 5FuJmv0R5k2klSVKk1E7RbipuwBA1ce0Nup0A7l/JkfbtPul87Y1bvqUnByZIT8Xdzbv j99rwiT0zWXvfyjDCtxjiQ6Lxt8UkrRwNSRKSC+gFQvZGK1yoTFx6+Sw+Ghw+4RwOdY+ oZmw== X-Gm-Message-State: AE9vXwNw8Q72w3xabYqRf0JU1AKLb86M/mmQYLtSrTI3VkeME44N3MI4Rn1uPX9bvNci5tQ45Jd8efFlo1fC+w== X-Received: by 10.107.184.131 with SMTP id i125mr30195038iof.167.1474955922497; Mon, 26 Sep 2016 22:58:42 -0700 (PDT) MIME-Version: 1.0 Sender: wlosh@bsdimp.com Received: by 10.36.65.7 with HTTP; Mon, 26 Sep 2016 22:58:41 -0700 (PDT) X-Originating-IP: [69.53.245.200] In-Reply-To: References: <20160926150109.0d0d793e@hermann> <57E92726.2020605@gmail.com> <5484D815-4B17-456B-BA60-CC6F4E97AFE3@gmail.com> <1785064.lgVzRW13Wf@ralph.baldwin.cx> From: Warner Losh Date: Mon, 26 Sep 2016 23:58:41 -0600 X-Google-Sender-Auth: Z3jQEyPCMwN824yoEnXgowSu8Is Message-ID: Subject: Re: Destroy GPT partition scheme absolutely, how? To: "O'Connor, Daniel" Cc: John Baldwin , FreeBSD Current , Ngie Cooper , Ernie Luzar , "Hartmann, O." Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Sep 2016 05:58:43 -0000 On Mon, Sep 26, 2016 at 11:06 PM, O'Connor, Daniel wrote: > >> On 27 Sep 2016, at 14:28, Warner Losh wrote: >> dd of 2MB of zeros to the start and end of the disk. That will destroy >> pretty much everything. For SSDs, sometimes you can do the same with >> TRIMs only faster (other times they are slower or unreliable). > > Yeah, but it would be nicer to not have to know that particular magic incarnation :) Disk formatting has always been 3 parts magic, 2 parts luck and 1 part skill :) It doesn't fit nicely into geom because metadata can live elsewhere. I forgot to add the caveat not to try this on a disk that is part of a RAID volume. Warner