From owner-freebsd-questions@FreeBSD.ORG Mon Aug 25 20:25:40 2014 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 2E73DE7A for ; Mon, 25 Aug 2014 20:25:40 +0000 (UTC) Received: from mail-oi0-f47.google.com (mail-oi0-f47.google.com [209.85.218.47]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id EBC9738A1 for ; Mon, 25 Aug 2014 20:25:39 +0000 (UTC) Received: by mail-oi0-f47.google.com with SMTP id x69so10007984oia.20 for ; Mon, 25 Aug 2014 13:25:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=wyg4vhL0P5At3PyWYzSBEP0uy2tX5uRXlZJhhTABvdM=; b=jRMkAQecSyCuSICOdIDucD3C/DdInIlu60/Vrr8xnZ3LGrXjK3rXovj/pLz11i7Jte rLg0vm4+teZp65J9Q0YDC4O8BL50mzFT644oN1ONqolWhvlt4Y88jY0z0/AANMuvfOUe +nvqAtQjdRiuDHr/BMcFz3cCQjrxdZPjqSBJxtqZtAPD5cakPB/ihjIcEvzcyrSH1w8H v4qMMlkBBgZMfyXboRqR8ttqZrpJDy0+og57wdj22qlwQcqnb0PPV/0TDx7IiX9QcE44 TlZyEwsHc2ZbEvD89N8V7mx1wgLgNdiqrYoObXoXnGInmyhmbbqGvQEesWfzteAnDI1m Zrqw== X-Gm-Message-State: ALoCoQkgyrziqw0ahFMf6JchhTiuP+GsemptQeiTOx7J5rupAGvH484hdzJWQtKdAa6POE+L43X0 MIME-Version: 1.0 X-Received: by 10.182.87.167 with SMTP id az7mr23621979obb.41.1408997943211; Mon, 25 Aug 2014 13:19:03 -0700 (PDT) Received: by 10.60.120.37 with HTTP; Mon, 25 Aug 2014 13:19:03 -0700 (PDT) In-Reply-To: <20140825182440.GA57059@slackbox.erewhon.home> References: <201408070816.s778G9ug015988@sdf.org> <40AF5B49-80AF-4FE2-BA14-BFF86164EAA8@kraus-haus.org> <201408211007.s7LA7YGd002430@sdf.org> <20140822005911.GA52625@neutralgood.org> <201408241027.s7OARfEK004658@sdf.org> <53FB0AFD.6010507@cyberleo.net> <20140825182440.GA57059@slackbox.erewhon.home> Date: Mon, 25 Aug 2014 13:19:03 -0700 Message-ID: Subject: Re: some ZFS questions From: Michael Sierchio To: FreeBSD Questions Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Aug 2014 20:25:40 -0000 On Mon, Aug 25, 2014 at 11:24 AM, Roland Smith wrote: > With modern drives the data density is so high that it is almost impossible to > retrieve single overwritten bits, let alone bytes or files if the complete > disks was filled with zeroes. That is unfortunately naive - all modern drives, whether spinning platters or SSDs, silently remap sectors when they detect incipient errors, for wear leveling in the case of SSDs, etc. This means that it is possible for someone with direct access to the disk to recover whole sectors - sectors that you cannot erase, no matter how many synchronous writes you perform in the OS. - M